Some good books for you to consider:
The Blind Watchmaker by Richard Dawkins (A clear and persuasive description of evolution)
The Orthodox Corruption of Scripture by Bart Ehrman (This is Ehrman's first popular book and in many ways his best. Talks about how the text of the NT was altered at the very earliest stages)
The Better Angels of Our Nature by Steven Pinker (Everyone leaving JWs should read this book because it dispels the myth than humanity is going to hell in a handcart. I've not managed to read all this book, it's very long, but Pinker is easy to read and the points he makes are valid)
The Jehovah's Witnesses: Portrait of a Contemporary Religious Movement by Andrew Holden (gives a social science explanation of the phenomenon of JWs as well as those who leave, good for giving perspective)
Combatting Cult Mind Control by Steven Hassan (good for understanding how control techniques used by JWs are common to other groups)