Here's a short list of books I put together that I think represent the case for atheism very well.
Any atheist that is serious about his/her lack of faith should read at least some of these books. They aren't light reading though. But I've found that as I read these, I tended to read them faster and faster as they are such damn good books.
Being an atheist is easy but being informed about it and being able to defend it well are important things. We can learn a lot from these authors though. They're leading the charge.
The Blind Watchmaker
The God Delusion
god is not Great: How Religion Poisons Everything
The End of Faith
Letter To A Chrisitan Nation
Breaking the Spell: Religion As A Natural Phenomenon
Victor J. Stenger
God: The Failed Hypothesis
Why People Believe Weird Things: Psuedoscience, Superstition, and Other Confusions of Our Time
Why Darwin Matters: The Case Against Intelligent Design
The Science of Good and Evil: Why People Cheat, Gossip, Care, Share, and Follow the Golden Rule
John Allen Paulos
Irreligion: A Mathematician Explains Why the Arguments for God Just Don't Add Up
I know I'm probably missing some good ones. Any suggestions?