Name One Book That Changed Your Life (Your Favorite Book)

I'm always searching for new books to read, and I'd like for you to share one book that has changed your life for the better! I'm in the process of reading The Millionaire Mind by Thomas Stanley. I enjoy books on finance, success, entrepreneurship, ect. although it doesn't have to be limited to those topics!

Share your thoughts so that others may benefit!

Thanks in advance, 
-Justin from Maryland