What book out there have you read that really has changed the way you perceive the world?

I want to know what books the collective has read that has had a large impact on the way they think. A book that you began reading as one person, and ended reading as another. I know for me one of the books I’ve read in this vain was a self-help “quit smoking” book (Allen Carr’s EasyWay.) I know it’s somewhat benign, but it transformed an aspect of my thinking.

I’m hoping the collective knows books a little more profound (whether philosophically, or in whatever manner). In fact, I know you all will.