This is a little different to the rest of the suggestions here, but the nerds amongst us will no doubt be kicking themselves THEY didn't suggest it.
The book you have to read is known in common parlance as GEB, or more formally,
Gödel, Escher, Bach: an Eternal Golden Braid.
The linked article will expand on the content of this book, but to summarize it for you, if you take time to really read and understand GEB, everything you know about life itself will change. A pretty bold claim, but absolutely true nonetheless.
A warning: GEB is heavy going. Seriously. It's not a book to be taken lightly. There are courses at universities that dedicate an entire year to reading and studying this book. You, of course, don't need to take that long to read it, but when you're reading it, you're going to have to concentrate, and anything you don't understand, go back over. The author is remarkably adept at explaining some seriously complex shit in understandable terms, but even still, you're dealing with shit like set theory, mind-fucking paradoxes, isomorphism and the very nature of consciousness itself, from a mathematical perspective. Of course, if you make the effort and do get through it all, it will be one of the most rewarding experiences of your life, and as I already mentioned, your outlook on *everything* will change, not because it's full of mystical and spiritual wonder, but because goddamn, this book explains the fucking universe, and lets you in on the secret.