To David Eller, an atheist is someone who does not believe in any God, as opposed to someone who affirmatively denies the existence of God. People, according to Eller, are not born believing in God; they have to be converted. In Eller's terminology, we are all natural atheists, hence the title of this worthwhile and well reasoned book.
Eller's intention is to convert you back to your natural atheism. He even offers a twelve-step program; it won't work, of course, but neither do any other twelve-step programs, as far as we can tell.
The book runs the gamut from reasoning and philosophy to science and religion, toleration, separation of church and state, and (although he doesn't call it that) epistemology. Many of the subjects are at least vaguely familiar to me, yet I found Eller's treatments refreshing and worthwhile.
The book is a wonderful combination of reasoned argument and cogent one-liners. You'll have to read the reasoned arguments for yourselves, and I recommend you do so, but here, paraphrased, are some of the insightful one-liners. To the charge that atheism is a religion, Eller responds that atheism is no more a religion than not collecting stamps is a hobby. To monotheists, Eller (an anthropologist) observes that countless cultures believed in countless gods, and monotheists disbelieve in all but one. Atheists thus disbelieve in only one god fewer than monotheists. Finally, religion has no methodology and cannot solve problems: physics debunked phlogiston, but the Protestant Reformation could only replace one paradigm with a welter of conflicting paradigms.
Two criticisms: Eller's inconsistent use of "god(s)" for "God" drove me crazy. More importantly, the book has no index; unlike a fish without a bicycle, a nonfiction book without an index is considerably less useful than the same book with an index.
Such carping aside, it is a splendid book, and I highly recommend it.