Hells Angels by Hunter S. thompson
The Bike Riders by Danny Lyon( not a novel,mostly a photojournal, but awesone none the less)
Zen and the Art of Motorcycle Maintainance by Robert Pirsig
Jupiter's Travels by Ted Simon
The Motorcyle Diaries by Che Guevara (don't care if you don't like his politics, its an awesome sread)
Oh, and Mouse on a Motorcycle (for the kiddos or adults) by Beverly Cleary