I just finished Richard Dawkins' now classic The Blind Watchmaker. Not a bad book at all. But before I tell you about it I should provide some background.
I have a degree in English and American Literature and my minor was in History. In other words, I'm not great at science or math. But I've always been interested in some aspects of science and biology and evolution happen to be subjects I like. I'm not a complete moron when it comes to scientific subjects but I'm sure any 8th grade science geek could probably run rings around me.
Consequently, this book by Richard Dawkins is made for me. The way I understood it it was written with a general reader in mind. The book is well written and plausibly argued. And as long as you pay attention and follow the logic of the author's arguments it's not that hard to follow.
The basic premise of the book is to show how life could appear in the universe without a creator or any pre-conceived notion of design (the whole "Intelligent Design" argument now being debated across the U.S.). Dawkins obviously loves Darwin and bases his argument on cumulative evolution over billions of years (the age of the Earth [and please shut-up you stupid creationists trying to argue that the Earth is only 6,000 years old!]). Dawkins patiently explains how such a slow and random process like natural selection could evolve our life-forms over vast amounts of time. Like I said, I'm no great scientist, but the argument makes perfect sense and I still fail to see why anyone tries to argue otherwise (except, of course, for religious reasons, but those are very silly reasons).
Overall, this is a good way to try to understand evolution in more depth than the few words hopefully given to you in high school and college. There are a few parts which I found to be boring (like the taxonomy debates and different schools of thought in taxonomy) but I think this book is an important read--especially now that religious nuts are trying to dumb people down.