I'm of the Catcher in the Rye camp. I know it's very mainstream and therefore I am a dick, but it genuinely changed my life. I remember lying in bed, with snow falling heavy outside, reading the book whilst I should have been at sixth form. It hit me in a way no other book has.
My DP was equally moved by To Kill A Mockingbird and wants to give our first born son the middle name Atticus, but that's a different thread but I didn't feel particularly enamoured by the book.
So which books have changed your life, and why? What should I read to have another heart-stopping, existence-questioning moment?