Phil Zuckerman did well in writing this book. Granted that it is not new or unique in its claims, it is good to see that some more research is being done on issues such as conversion and apostasy. This book gives a glimpse into the beliefs and journeys of "ordinary" atheists which is really needed since polemic atheists like Richard Dawkins, Sam Harris, Christopher Hitchens, etc are simply not representative of the vast majority of atheists' attitudes, beliefs, and intensity. This book is a decent place to start for those who are interested in what triggers apostasy and what has made some who subscribed to one belief system abandon and switch for another. He interviews 87 people total in this qualitative study (about half were raised in California and the rest are from other parts of the country or other parts of the world). Christian apostates are the main focus in the book, though others are mentioned. For many, atheism and agnosticism became their new belief system (I would argue "religion") since just as they left a few beliefs and behaviors they also gained quite a few to substitute or replace them. Its good for some to know that atheists and agnostics do not live empty lives that are void of content. They have beliefs like everyone else. In fact, atheists are simply not qualitatively different than theists.
This book is mainly about atheists and agnostics and how or why they ceased believing certain things they used to. It is clear that most of the abandonment of previous beliefs had very little to do with rigorous analysis of the best scientific and philosophical arguments and research. Instead, the core drives for the abandonment of their previous beliefs were subjective reasons such as biases, personal experiences and expectations, social or personal loss, and other subjective inclinations. This is pretty much in line with recent research on how people develop beliefs The Believing Brain: From Ghosts and Gods to Politics and Conspiracies---How We Construct Beliefs and Reinforce Them as Truths. Also other qualitative studies on loss of faith and conversion to atheism or secularism from other countries show similar correlations. Chapter 5 of Varieties of Unbelief: Atheists and Agnostics in English Society, 1850-1960 qualitatively reviews 150 conversion experiences of secularists within 100 years (between 1850 and 1960) and notes that the conversions to atheism and secularism were due mostly to individualism; moral, social, and political reasons such as injustice; or family related; not scientific or theological or philosophical reasons. In other words, conversions are more moral based than intellectual.
It appears that some of the apostates interviewed in Zuckerman's book had very strange habits or expectations in terms of prayer, divine interference, and compensation for their devotion and commitment to their "religions". It is also clear that many struggled in their departure and some experiences from their youth seemed to have had a major impact on their adulthood and apostasy.
I will note a few things from the main chapters:
Ch. 1 - there is some discourse on people who had an exorcist mother and how that impacted them.
Ch. 2 - focuses on how some began to see inconsistencies between their beliefs and experiences in life.
Ch. 3 - focuses on misfortune such as loss of loved ones, trauma, unanswered prayers, injustice, divine karma failure (where many felt they did everything right to please God, expected God to repay them with good rewards, but instead had misfortune fall on them).
Ch. 4 - ex-Mormons and repercussions they experienced after dropping out ; gay issues and its influence on some of the apostates (apparently about 1/3 of the interviewees mentioned anti-gay views as a key ingredient in their apostasy).
Ch. 5 - focuses on sexual influences and experiences, usually in their youth, that were "crucial", but not always significant in their apostasy.
Ch. 6 - focuses on experiences of hypocrisy and immorality as an often cited contributor for apostasy. Exchanges with other cultures and worldviews and their impact are also discussed.
Ch. 7 - focuses mainly on two women that are exceptions to some studies expectations. They were poor, had problems like drug abuse, and suffered quite a bit; but though both used to believe in God, they no longer do and have gained some control in their lives.
Ch. 8 - focuses on mainly supporting ideas like people without god-beliefs can be very moral (he argues that they can be more moral than religious people on certain measures), they have a meaning in life, they can deal with death, they can feel liberation and autonomy, and notes things apostates sometimes lose when they abandon their previous worldviews. He discusses some negative stigmas that are often placed on atheists such as being angry, sociopathic, loveless, etc. Some of this is not far from the truth, but much of it is not reflective of the characteristics of ordinary atheists. Some of the atheists seemed to down play their previous beliefs a little too much that it leaves one with an impression that their previous experiences, as believers, were worse than they really were. Surely they stuck to their beliefs for a long time, so it cannot be that they really had experiences that were THAT bad, because if the experiences really were that horrific, then the apostasy would have occurred earlier. It sometimes sounded like a couple that just had a really bad divorce - finger pointing and poor self-criticism - even though at some point they did have degrees of attraction.
Ch. 9 - focuses on the impact that the parents had on the apostates. Zuckerman notes that many had at least one parent who was not "religious" or at least indifferent to such topics. Interestingly, he notes that some want their own children to be "religiously" involved. Other parenting issues are discussed.
Ch. 10 - focuses on apostasy as a process involving many factors, not just one. Not all interviewees were atheists, some saw themselves as "spiritual", or even believing in God in their own way. Some factors or reasons influencing apostasy included:
* Parents - many had one parent as "religiously" involved and the other was not or indifferent. The lack of balance among both parents does impact the probability of apostasy.
* Education - exposure to other ideas may create competition for personal beliefs
* Misfortune - loss of loved ones or issues like divorce may push some to reconsider their beliefs
* Other Cultures and Religions - exposure to other ideas may provoke reconsiderations of their beliefs
* Friends and Acquaintances - sometimes speaking to others leads to deep discussions or questions that may provoke reconsiderations of their beliefs
* Politics - issues and moral inclinations in light of things like the "religious right" or liberalism
* Sex - desires of the flesh vs control of the desires
* Hell - conflicting with personal views
* Hypocrisy - with "religious" leaders, family, or acquaintances
Zuckerman notes that these "reasons are not necessarily causes" and correctly notes that most people who deal with these same factors are not apostates at all but are believers and remain believers. Usually these factors strengthen or at least are not enough to make most people abandon their beliefs.
Some background data: In the Introduction, Zuckerman notes different types of apostasy in the introduction (shallow, deep, mild, transformative, early, late, etc). He also notes that the number of those who classify themselves as "Nones/No Religion/Unaffiliated" in religious identification surveys, such as ARIS, has increased from 8 % in 1990 to 15 % in 2008, however, it needs to be added that by 2001 the "Nones" had reached their biggest burst of 14.1% according to ARIS data. It has apparently leveled off since then. The major increase from 8 % in 1990 to 14.1 % in 2001 is due to people distancing themselves from the political image of the "religious right", not increase in "religious" skepticism or more atheists and agnostics, because the majority of "Nones" are simply "unchurched believers" (Fischer, Claude and Michael Hout. 2002. "Why More Americans Have No Religious Preference: Politics and Generations". American Sociological Review 67(2): 165-190). They are the ones that increased the "Nones/No Religion/Unaffiliated" demographic. From the time that books by the New Atheists got really popular and got significant momentum, from 2001 to 2008, there was only a .9% increase in "Nones" (14.1% in 2001 to 15% in 2008) which is incredibly small for 7 years. Obviously not all of these were atheists and agnostics either.
Update 4/18/14 - In the new data from the Pew Research Center from October 2012, "Nones" have gone up to 19.6% of the American population, as of 2012. However, out of that demographic only 12% of the "Nones" are atheists, 17% are agnostic, and 68% believe in God (a universal spirit). The majority are still "unchurched believers". Overall atheists made up 2.4% and agnostics made up 3.3 % of the total US population in 2012. Interestingly enough according to the Pew data, the religious are not more prone to believe New Age beliefs than the non-religious. Interesting data. According to Gallup data from 2012, the number of "Nones" is 17.6% of the total American population and there was a slowing down recently. So from 2001 to 2012 the number of "Nones" just went from 14-15% to 18-19% with "unchurched believers" making up the bulk, as usual. This implies that any secularity observed is more likely to be a by-product of structural changes, not intentional activity such as religious skepticism.
The actual number of Americans who do not believe in God is constantly between 2-5% on all national surveys (Gallup, Pew, ARIS, etc). Atheism is a very small demographic indeed. However, interestingly the 2008 report from the Pew Research Center says clearly that "5% of American adults say they do not believe in God or a universal spirit, but only about a quarter (24%) of these nonbelievers actually call themselves atheists." The same report notes that agnostics make up only 15% of those who do not have belief in God or a universal spirit. This means that 61% of nonbelievers self identify as something else besides "atheist" or "agnostics"! Truly people's identities and beliefs are quite complex.
Anyways, back to the review, limitations in research is expected. For example, some of the studies Zuckerman cited in Ch. 7 with "religiosity" and dimensions of education levels were not as recent or as diverse as I hoped. For example, ARIS data from 2008 on people with post-graduate degrees shows that they are very similar demographically, in terms of religiosity, to the general American population and that religion and post-doctorate degrees are both independent variables meaning that religiosity and higher education do not affect each other as Enlightenment thinkers presumed (Kosmin, Barry. 2010. "Religion and the Intelligentsia: Post-graduate Educated Americans 1990-2008"). He notes that the empirical data does not support the hypothesis that those with the post-graduate degrees are more prone to have an Enlightenment mentality and be less religious. He notes, "The only sign of greater secularization is more support for the theory of human evolution but there is no evidence of a dominant "atheistic naturalism"." Indeed, one of the biggest national samples taken on US professors' beliefs, including those in the sciences and humanities, summarized "Contrary to the view that religious skepticism predominates in the academy, we find that the majority of professors, even at elite research institutions, are religious believers." (Gross, Neil and Solon Simmons. 2009. "The Religiosity of American College and University Professors". Sociology of Religion. 70(2):101-129). Simmons and Gross' data shows that natural science professors have less disbelief in God than social science professors though there is more agnosticism instead, for the natural scientists. This shows that religiosity by academics is very complex and not reducible to 'science education automatically leads to a clear rejection of theism'. The book "Christians Are Hate-Filled Hypocrites...and Other Lies You've Been Told: A Sociologist Shatters Myths From the Secular and Christian Media" (product link at the bottom of the review) provides recent Pew Center data on these issues and concludes that evangelicals that have higher education such as college and graduate degrees have higher "religiosity" and that numerous religious groups have either average or higher levels of education than the nonreligious. Similar findings from recent research trends among young people are noted in the book "Souls in Transition: The Religious and Spiritual Lives of Emerging Adults" (product link at the bottom of the review).
In terms of public perceptions of science: "Religious" America has the same science knowledge base as "Secular" Europe; the US has more interest in science than Europe; the majority of Americans show strong support for the sciences and funding research; Americans visit more informal science institutions (i.e. museums, zoos, etc) than European and the Japanese; Americans have more favorable attitudes towards science and technology than "more" secular regions like Europe, Russia, and Japan (National Science Foundation. 2012. "Science and Engineering Indicators 2012" Ch.7). Other studies on views of science and religion, which pooled data from many countries from 1981-2001, have noted that countries with higher religiosity have stronger faith in science than "secular" countries and that "secular" countries are more skeptical toward science and technology (Norris and Inglehart. 2011. Sacred and Secular: Religion and Politics Worldwide (Cambridge Studies in Social Theory, Religion and Politics) Ch.3). More international studies are available (Bauer, Shukla, and Allum. 2011. The Culture of Science: How the Public Relates to Science Across the Globe (Routledge Studies in Science, Technology and Society)). Predictably, one find here is that even "strict creationists" in America have very positive attitudes towards science.
Interestingly, research on adult scientific literacy consistently concludes that Americans usually score above all other nations in international rankings of adult scientific literacy since he started his research in 1988 (Hobson, Art. 2008. "The Surprising Effectiveness of College Science Literacy Courses". Physics Teacher 46(7): 404-406). Recent sociological studies confirm that conservative religious people have no epistemic conflict with science and they do not differ in propensity in seeking out scientific knowledge than nonreligious groups, only minor issues may emerge when scientists make moral agendas (Evans, John. 2011. "Epistemological and Moral Conflict Between Religion and Science". Journal for the Scientific Study of Religion 50(4):707-727 ; Baker, Joseph O. 2012. "Public Perceptions of Incompatibility Between Science and Religion". Public Understanding of Science 21(3): 340-353 ; Keeter, Scott; Smith, Gregory; Masci, David. 2007. "Religious Belief and Public Attitudes About Science in the US". Pew Research Center). Research on most college students indicates that the majority of undergraduates from the natural and social sciences in college do not see conflict between science and religion either despite that conflict narrative being taught there often (Scheitle, Christopher. 2011. "U.S. College Students' Perception of Religion and Science: Conflict, Collaboration, or Independence? A Research Note". Journal for the Scientific Study of Religion 50(1):175-186). In the "Nones on the Rise" (2012) Pew Research Center report (p.24), it is noted that the nonreligious are no more likely than the religious to have New Age beliefs and practices.
---Some of the assumptions I read in Ch. 8 did seem odd to me. It could be seen that Zuckerman was being too apologetic of atheists and morality. He lumps "religious" people as if they were congruent in beliefs, belonging, and behavior when he compares them with "secular" people such as atheists. He should not lump "secular" people and assume congruency either. "Religious" and "secular" people are both very diverse. For instance, not all atheists deny the supernatural (Buddhists, Taoists, Confucianists, indigenous religions). The diversity cuts both ways and both have significant overlap since every religious "thing" has its secular corollary. For example, it does not do justice to the research to ignore the overwhelming secular nature of "religious" people since much of the "hypocrisy" and "immorality" that can be identified with religious people has a secular nature and foundation (e.g. Catholic priest molestations were definitely NOT done for the sake of Christianity or the Catholic Church). For sure, to be secular is not necessarily like Phil Zuckerman characterizes constantly - as irreligious and/or naturalistic - since in reality "secular" simply means "of a generation or of the world" etymologically. Just by analyzing people who are quite "religious" one would have to notice their secular nature and how they constantly interact and are influenced by this world. They really are not as "other-worldly" minded as is often assumed.
Overall, this book deserves a wide audience. For more on diverse issues please read:
Atheism and Secularity [2 volumes] (Praeger Perspectives) (sociological data on the beliefs and characteristics of atheists worldwide)
Atheists: A Groundbreaking Study of America's Nonbelievers (another sociological study on beliefs and characteristics of atheists)
There Is No God: Atheists in America (another sociological study on beliefs and characteristics of atheists)
Christians Are Hate-Filled Hypocrites...and Other Lies You've Been Told: A Sociologist Shatters Myths From the Secular and Christian Media (since Zuckerman commented on Christianity often in this book, it is good to contrast his conclusions and claims on Christians with sociological data on Christians on many topics)
American Evangelicalism: Embattled and Thriving (sociological research on evangelicals and fundamentalists on demographics and key characteristics. One chapter  discusses doubts and defectors [nonreligious] and notes that 80% of them do not adopt a naturalistic or secular worldview)
Souls in Transition: The Religious and Spiritual Lives of Emerging Adults (since many of Zuckerman's interviewees mentioned details from their youth; it would be wise to look at the sociological data on multiple generational trends.)
"Who Really Cares: The Surprising Truth About Compassionate Conservatism" (since Zuckerman mentions moral issues, this research on Charity will be revealing. The core find was noted by Alexis de Tocqueville over 170 years ago.)
Finding Faith, Losing Faith: Stories of Conversion and Apostasy (a sociological study on apostasy and conversion including a section on atheists)
Atheist to Catholic: 11 Stories of Conversion (this book should give a contrasting look at people who are apostates of atheism and why some turn away from atheism)
For a good summary of when modern atheism spawned (17th century, not before), and the relationship it had with science up to this century one can see Oxford and Cambridge's review from the "Investigating Atheism" project website under the "Atheism & Science" section.