Dawkins is well known for his classic books like this one. It is a must read for anyone remotely interested in arguements for evolution and against "Intelligent Design". Dawkins was visionary by writing this book 15 years before the controversy began, giving credible weight to his far-sighted vision.
Although I already had a pretty good grasp of evolutionary theory before reading this book, I felt that this book greatly illuminated the finer points of evolutionary theory in general, and specifically those points where the proponents of creationism and/or intelligent design try to muddy the waters. It is extremely well written and entertaining as well. I love Dawkin's dry sense of humor which makes reading even very technical arguments interesting. However, if you are set on believing in god, you shouldn't read this book - I can't conceive of anyone reading this book, comprehending the material, and still being able to state with certaintly that there is a god.