This is an interesting thread. Thank you to all who have provided links to books I was not aware of. However, I would like to pose a related question.
I actually have never felt the need to justify my atheism. To me atheism has always been the simplest and most logical baseline. It should be incumbent on those who tout some of the more outlandish beliefs of various religions to provide justification for that.
On the other hand I don't see much point in books that are hostile to religion. Having read Dawkins and Hitchens I find that they, and Hitchens in particular, put too much blame on religion for the world's woes. Yes, Christianity has caused a lot of death and destruction, but nothing compared to that caused by greed and bigotry.
What I am more interested in is a book that discusses why so many people still believe in religion. I recall reading an article some time ago that suggested that this believe actually was part of our evolution. That belief in supernatural reward and punishment in this life, and perhaps even more important in an imagined limitless afterlife (there's and oxymoron for you

), helped coerce our evolutionary ancestors into behaviors that had rewards for species survival. I would be interested in a book that provided an expanded discussion of that idea.