I've been really into Haruki Murakami these days. Have you ever read him? "Kafka on the Shore" and "Wind-up Bird Chronicle" are my two favorites.
I've been really into Vonnegut lately. He can be heavy at times, but there's a jaunty humor in the way he approaches serious topics that makes it cruise-appropriate.
I'm afraid I'm a little boring....James Patterson is always fun to read on a cruise. I have also fallen in love with Darynda Jones with her Charlie Davidson as the Grim Reaper. Charlie is so much fun. My heavy reading is James Rollins with his Sigma Force Novels. Sista needs some fantasy because I live in too much reality. LOL!