Everyone knows that the answer to the Ultimate Question of Life, The Universe, and Everything is 42.
Well, everyone that read Hitchhikers Guide to the Galaxy.
http://www.douglasadams.com/creations/hhgg.html
The Hitchhiker's Guide to the Galaxy,
The Restaurant at the End of the Universe, and
Life, the Universe, and Everything are the good ones. I recommend
So Long, and Thanks For All The Fish if you liked the first 3.
The other books aren't that great and I only recommend them for diehard hitchhiker fans.
The series is probabaly the funniest books I've ever read. You have to really have a brain to understand the jokes (they are also british-oriented), but the books also really make you think in a different way.