This is the first Freud book I have ever read. I am not a trained psychiatrist, or sociologist, or ethnologist, so I am going to review the book from a layman's standpoint.
In this work, Freud draws heavily on observations and theories of ethnology, emphasizing on studies of Australian aborigines and Frazer's work. He draws a parellel with his personal observations from treatment of "neurotic" patients and claims to have found common patterns in these two classes of subjects, which tend to explain certain social and psychological phenomena, as well as the "birth" of religion.
He focuses on the concepts of "Totem" and "Taboo". While familiar with taboo (although our understanding of the term is narrower than Freud's), totem is remote to us. Certain aboriginal peoples were grouped in social groupings, centered on the cult of and belief of descent from a certain animal. So, you are the "Kangaroo tribe", we are the "Ostrich tribe" etc. The topic most interesting Freud, to which he devotes the first essay in the book, is "exogamy", i.e. marriage outside one's group. This practice of exogamy seems to be in contradiction to what is pursued by some ethnic groups in America (Jews and Greeks come to mind) i.e. "endogamy" - a push to have children marry within their parents' ethnic group. This practice of exogamy in Australian aborigines is attributed by Freud to fear of incest, with quite convincing arguments.
What is challening is to concoct a theory that suggests totemism and exogamy are not orthogonal social institutions that just happenned to coexist, but intricately bound together. Freud accomplishes that through intricate reasoning that draws heavily on religion (in his 4th essay). His argumentation may seem far-fetched to many, but is plausible, although it is hard to get convinced that it is the single, or most probable, theory explaining the issue.
Freud makes the analogy that what primitive people are to ethnography, "neurotics" are to psychoanalysis and tries to map patterns from one domain to the other. Another goal is to establish the theory of totemism as the primordial religion from which all known religions and beliefs have spawned over time. The fact that Hinduists rever and never kill cows, seems to me (my example, not Freud's) to support this theory; Hinduists could be considered an outgrowth of a "Cow totem". Also, in modern Judeochristian societies, the totem, for intermarriage avoidance, has been replaced by the blood relatives group. Greek civil law for instance, forbids marrying blood relatives to the 4th degree and relatives through marriage to the 3th degree (i.e. after marriage your also become a member of your spouse's "totem" - for life).
His 2nd essay discusses the concept of taboo. He defines it as "a set of limitations that primitive people apply to themselves". He contends that people who do "taboo things" become taboo themselves (certainly prostitutes would fit that profile). In our modern society, one's car is taboo, such as one's tools and guns were in prehistory.
Deists may have a hard time with Freud, especially since he states "we know well that just like gods, demons too are figments of the human imagination". Freud was an atheist and his train of thought is naturally and instictively atheistic, and this could be challenging for a deist.
Amazing is how some taboos of primitive times, remain alive, even in a degenerate form, in our times. For instance, just as primitives of New Guinea don't eat meat after killing an enemy (a taboo), modern Greek Orthodox people don't eat meat in the lunch following the funeral ceremony (only fish and veggies allowed). Also, the "dirtiness" taboo, where primitives were subjected to purification ceremonies, seems to be alive in the Eastern Orthodox sacrament of baptism where the to-be-christened baby is washed in the baptisery. Female "uncleanliness" during menstruation is also taboo in the Eastern Church; women are never allowed in the santum (blood taboo). It is considered taboo in Greek to say that a woman is menstruating, whereas politeness calls to say that "she feels sick". Also, the death taboo is alive in an incomprehensible to me (but "self-evident" to them as Freud would say) avoidance by many to refer to cancer by its name, opting instead the expressions "the bad thing" or "the cursed disease".
Also, the taboo, Freud mentions, whereby the archpriest of Zeus in Rome, was forbidden to ride horses, seems to be alive, in that the heads of states rarely drive cars themselves, but are rather given a ride by their chauffers. Regarding king-priests, last time I checked the Queen of England was also the head of the Church of England...
The third essay (animism and magic) is also important. Interestingly, Freud considers animism as the only weltanschaung completely and comprehensively (albeit incorrectly) explaining world's nature. He does not believe that subsequent religious and scientific weltanschaungen have achieved this. The animism->religion->science progression of world views discussed is extremely important and core for understanding his work. I guess that were he alive and learned that 90% of Americans are religious (Source: Euronews) he would be rather skeptical of the "progress" of mankind...
In his fourth essay, he returns to totemism, reaching the culmination of this work, in an awe-inspiring scene, where the young brothers kill and devour their own father. This vivid scene of patricide, which he subsequently manages to mitigate, suggesting the possibility that it was perpetrated only in people's minds (temptation), he proclaims as the original sin of mankind, which young males throughout the millenia try to redeem. This theory is highly controversial, albeit very interesting and thought-provoking. This scene is worth the whole book not only for its intensity, but also for the dexterity with which Freud creatively combines and correlates findings from fields so diverse, such as psychiatry, psychology, sociology, ethnology, religion, and philosophy, along with deep understanding of the human psyche, to reach a conclusion of such importance, and arguably impact, regarding who we are, and why we are doing things the way we are.