Kurt Vonnegut Jr. was one of the most influential writers of the twentieth century, with very dark and ironics novels (a lot of thought food). I discovered him when I was in university, and I quickly associated him with the Science-Fiction new wave great authors (Dick, Disch, Spinrad, …), but I think it was probably the correspondant of a faux-naive Montesquieu or Voltaire.
I love specifically three novels, Breakfast of champions
, from wich comes the Bruce Willis-starring movie, The sirens of Titan and Cat’s craddle (clic to read the synopsis of each of these books).
While I don’t care about the political position of this writer, which was a very prominent figure in the hippie generation, and recently, in the american anti-Bush coalition, I found these novels very inspirational - and, at least, darkly - but luminously - funny.

Kurt Vonnegut Jr. Wikipedia
Official website
The Vonnegut web
Rolling Stone article
L.A. Times
New York Times