The first book I bought to read on a cruise was SKINNY DIP by Carl Hiassen because I knew it involved (only to a limited extent) a cruise ship. That turned me on to everything else Hiassen wrote, and a friend turned me on to Dean Koontz.
I'll usually bring 2 or 3 books to read, then find I don't even have time for one!
Anyways, I have 3 books set aside for my next cruise:
MEL STOTTLEMYRE BIOGRAPHY (former Yankee pitcher and coach who battled cancer several years back)
SHIP FOR BRAINS by Brian David Bruns - followup to CRUISE CONFIDENTIAL, which was a humorous look at an American working on a cruise ship
SHIP HAPPENS by M J Kikker - a collection of limericks and jokes about cruising
I figure that should hold me. What's everyone else reading?