Dawkins begins by defining the subject matter of the book. He distinguishes between faith-based religion, and "Einsteinian religion," which is really no religion at all. Einstein, like many other scientists, such as Stephen Hawking, use the term God only in a metaphorical and poetic sense; this can lead to confusion. When Einstein said "God does not play dice," he meant something like "Randomness does not lie at the heart of all things," and when he asked "Did God have a choice when creating the universe?" he was really asking "Could the universe be any other way than how it is?". This metaphorical kind of "religion" and "God" is not the subject of the book. Dawkins is out to demonstrate that the literal, faith-based God is a delusion, and that religion in the literal sense is misguided, dangerous and discourages independent thought.
Chapter 2 begins with this amazing sentence:
"The God of the Old Testament is arguably the most unpleasant character in all fiction: jealous and proud of it; a petty, unjust, unforgiving control-freak; a vindictive, bloodthirsty ethnic cleanser; a misogynistic, homophobic, racist, infanticidal, genocidal, filicidal, pestilential, megalomaniacal, sado-masochistic, capriciously malevolent bully."Wow. This sets the tone for the whole book.
In chapter 3, he demolishes the arguments in favor of a literal God, such as the "proofs" of Thomas Aquinas, and the arguments from beauty, personal experience and scripture. In chapter 4, Dawkins shows 'Why There Almost Certainly Is No God". He presents the arguments for evolution by natural selection, clarifying many popular misunderstandings - such the belief that evolution is a "random" process - and shows that the existence of a Creator is unnecessary and extremely improbable.
Chapter 5 explains why religious belief came about, in terms of evolutionary psychology. Chapter 6 explains why moral genes were naturally selected and why religion is not necessary for morality and chapter 7 explains that even devout religious believers do not truly get their morals from religious texts, despite their claim to do so. This is because the major religious texts are self-contradictory and downright immoral in so many ways; religious believers must have some way of deciding which morals they will live by and which moral lessons they will ignore.
In chapter 8, Dawkins explains why it is important to question religion and faith-based beliefs, and not give them a 'free pass' and undeserved respect. Religion is a divisive, destructive subversion of science, and religious believers tend to be unthinking, unoriginal, fanatical, and gullible, accepting authority without question. In chapter 9, Dawkins argues that raising children with religious beliefs is a form a child-abuse and such mental abuse can be far worse than physical abuse.
Having demolished arguments for religion as an explanation (Chapter 4) and exhortation (Chapters 6 and 7) for human life, Dawkins briefly considers the role of religion as a consolation and an inspiration in chapter 10.
Overall, a fantastic and explosive book, recommended to anyone, religious or not.
There are various youtube videos of Richard Dawkins talking about this book and many of his other books. Here is one example, where Dawkins reads extracts from "The God Delusion" to students, many of whom are devout Christians. The question-and-answer session (part 2) is highly entertaining.