One of my favorite books in the past year or so:
The Reason for God, by Timothy Keller
This is great book for skeptics who have doubts about Christianity, as well as believers who want to better discuss their faith. The first part of the book deals with common doubts and questions people have about Christianity. The 2nd part of the book examines many reasons why Christianity is true and is a better and more reasonable explanation for the big questions in life than any other belief system. A very helpful book!