I am very fond of
Why Won't God Heal Amputees?, which provides a very accessible, friendly, throughout argument from the problem of evil for why God doesn't exist. I particularly like its empiricist bent and focus on evidence (not in the narrow sense of scientists in laboratories with lab coats and expensive equipment, but in the sense of what everyday occurrences we would expect to see and not expect to see if God were real, and how those predictions don't match up with reality). The last two chapters are atrocious, though; I really wish they were cut from the book. They are grand proclamations about the meaning of life, the future of humanity, and how to live your live without religion; and rather than being advanced with the care he took to lay out his arguments earlier in the text, they are instead laid down on from on high as if they were the word of God. And the sad thing is that I don't actually disagree with him all that much, but I nevertheless dislike them because the material is extraneous to the main point and poorly justified.
Then there are also books which specialize in attacking the
Bible. Two good ones are the
Skeptic's Annotated Bible and
The Brick Testament. The
SAB reprints the text of the
Bible and makes marginal notes whenever something worthy of attention, such as sexism, happens to show up in the good book.
The Brick Testament, on the other hand, is brilliant in that it adds virtually nothing to the original text; it just illustrates the verses in an unabashedly literal manner and makes them easy to read, and yet that is still enough to get people riled up. Keep in mind that it contains graphic depictions of lego figures having sex and being dismembered, though, if you are offended by that sort of thing.
If you want some more advanced material, this is isn't a book, but there's a great blog which has
a bunch of posts grouped together under an "antitheism" tag which you may find interesting (and
two more posts that are not under the tag, but still relevant).
Finally, as far as Dawkins goes, I read (listened to, actually)
The God Delusion and found it very disappointing. There are several reasons for this, from his choice of argument for "why there almost certainly is no God" (the Ultimate Boeing 747 is not a bad argument, but is rather overhyped), to his lack of a detailed thesis to follow through the book (splitting it into an argument against God half and an argument against religion half doesn't count), to his invocation of
Immanuel Kant for the morality chapter (of all people...), to his judgement that "the God of the Old Testament is arguably the most unpleasant character in all fiction" without following up with
immediate justification for why that is so (he is not necessarily wrong, but he can't just say that without explaining the reasoning to his religious readers), to the focus on biology and cosmology as opposed to the more cultural aspects which he only gets to towards the end of the book. I think the book would most useful to a scientifically inclined kid who had just become an atheist and thus hadn't had time to learn a lot of the standard material criticizing religion. Atheists with more experience will know most of what Dawkins says in the book and find it boring, while religious people will perceive most of it as attacks because he doesn't manage to make a good enough case for it.