These won't make you think afterward, but for light vacation reading:
Crime/mystery - John Sandford's Prey novels
Fantasy/Sci-Fi - Jim Butcher's Dresden Files books. You need to start at the beginning with these, and they are very tongue in cheek. I like them for the pure escapism, and for the secret lab you'll learn about if you read them.
Sci-Fi - Jack McDevitt or maybe Kim Stanley Robinson's Mars books
Or light horror with Dan Simmons or James Herbert.
For fiction that's more literary, but still entertaining, I like Robert Girardi -- particularly "Madeleine's Ghost"