What book impacted your walk with God the most?
Although it's hard for me to choose, if I had to pick one that wasn't the Bible or Alcoholics Anonymous, it would be Mere Christianity by C.S. Lewis. I recommend it for anyone who wants to learn the fundamentals of real Christianity. Rich with metaphors, Lewis attempts to use reason and logic to prove the existence of God, and to argue for the divinity of Jesus Christ. It's an oldie, but a goodie!
How about you? What book changed your life after reading it?