Overall, I loved this book. Dawkins is a wonderful writer and I think I would have enjoyed his style regardless of the subject matter. The only major flaw that irked me was his habit of veering off into tangents, but even this was made bare-able by not only his writing style, but also by the fact that most of his tangents were just plain interesting. Dawkins makes his case even stronger, in my opinion, by fulling admitting to and even going out of his way to point out the limits of his own personal knowledge. At several times during the book, he will say that he suspects one thing but does not know for certain, showing an inquisitive and flexible mind, both humble and confident. It's a refreshing break from the average writer who seems all too sure of her/his omniscience.
With all that out of the way, I'd like to address a couple of issues with the book. The first is with Chapter Four or "Why There Almost Certainly Is No God." I found the whole chapter to be a disappointment. Dawkins takes the question of "if there isn't a god, how did everything fall into place so perfectly to produce us?" and tries to answer it with science. This points him in an awkward and unnecessarily defensive position because the question itself is not a legitimate one (something he never once says outright). It's like asking "how did my parents know to have sex at just the perfect time to conceive me?" It assumes that we are an end result, a goal that the universe has been working towards - rather than the more accurate assumption that the universe is merely ambling along in one of billions (to pick an unrealistically small number) of possible ways and we just happen to be a bi-product (one of many possibilities) that happened to emerge. There is nothing special about the production of us, whether as individuals or as a species.
Another quibble I had with the book is that Dawkins repeats multiple times that natural selection gets rid of negatives and keeps positives, which is just sloppy. What about the vast majority of mutations, which are just neutral? Or mutations that have both positive and negative expressions?I understand the need for brevity and keeping things simple, but this is a major point and something that a lot of Dawkins's opposition can't seem to grasp.
And the final detail that I took issue with is his statement that "[monogamy] is what we expect, and it is what we set out to achieve." Is it? Maybe he's right, I don't know. Maybe monogamy really is the default. But that's not what even the quickest glance around the diversity of human societies in the world today will tell me. Many societies involve one man and several women, some even involve one woman and several men. If monogamy truly is the natural default, why isn't this expression universal? Like I said, maybe he's right - but because his statement was counter-intuitive, the existence of polygamous societies should have been addressed.
With all that said, this was a fabulous book and I am very glad that I've read it. It ought to have stayed on topic a little better, but that's okay. There were no parts of the book that I felt weren't worth reading and that's more than I can say for most books.