I'll shamelessly admit that I really enjoy reading the Stephanie Plum mysteries by Janet Evanovich while traveling. They are interesting, engaging, funny, etc.
A woman once passed me on her way to the airplane lavatory (I had an aisle seat) when I was reading one, and I was laughing out loud. On her way back from the lav, she asked what I was reading. When she saw what it was, she said, "Oh, of course! Those books make me laugh out loud too!"