The Hitchhiker's Guide to the Galaxy by Douglas Adams
The one and only book you'll ever need if you happen to decide to travel the Universe - and check out the towel in my Nerd-gasm list, the second most necessary item for your cross galactic spree... Besides being a Universal Guide - you will also find "THE ANSWER" TO THE MEANING OF LIFE inside these pages... P.S. you cannot call yourself a respectable nerd unless you have read this.
Everything you ever needed to know about how to survive outside of Earth should the world blow up and you need to find a some new digs.