Why I am an Atheist Who Believes in God: How to give love, create beauty and find peace by Frank Schaeffer
Originally written on goodreads while 30,000 feet over the east coast.
Like someone else said, the book is full of one liners. As I tweeted my way through the book, you could see how offended dogmatic people were by the title.
If you can make it past the title, though, you will find that he has written an book full of honest uncertainty, one that shows how you can give up on the certainty of youth without becoming lost in cynicism and bitterness.
A longer, more cogent review is in The Daily Beast.