I'd second anything by Pratchett. The Discworld books are often sadly overlooked or dismissed by the highbrow tolkien crowd (their loss). Terry's sense of humour is blacker and drier than coal, and always an easy read.
For Sci-Fi I'd recommend some of the Warhammer 40,000 books. Not all of them as they can be very samey, but for a good strong plot, excellent characters, and a fine dose of asskickery, anything by Dan Abnett will serve well - Eisenhorn and Ravenor are detective and desciple respectively. They chase down powers that stupidly outnumber and outgun them, and Gaunts Ghosts has been described as "Sharpe in space".
Currently reading Terry Brooks "Running With the Demon" post apocolyptic meets fantasy... and....
"The Watcher" by Charles Maclean - surreal psychological horror about a man who commits a terrible act, but doesn't know why he did it or what is real or hallucination any more.