I am behind on my posting. Vjack posted an Atheism 101 Reading List a few days ago. His post is an excellent introduction to some of the most significant books on atheism available today. I've read them all (The God Delusion was a hard read, it took weeks).
I would add that if you are a blogger and read any of these books. Take the time to post a review. Book reviews are a great way to connect with other readers. But be prepared for criticism, people tend to take sides on books... and defend them to the death!
