Generally, anything by Dawkins is good, and highly scientific.  The primary origin of most of my concepts posed here come from, as you might expect, "The God Delusion".  This book is much less focused on science, more focused on history, but equally brilliant.

 For a more biting criticism of religion, check out Christopher Hitchen's "God is not great: how religion poisons everything."  Personally, I preferred this one. It's basically atheism with balls.