I agree with everything that has been said about the order in which to read the Culture novels. Consider Phlebas is definately earlier, but they can be read in any order. The short story in The State of the Art brings in present day Earth, so puts the rest into a context time-wise. I like Use of Weapons, and Player of Games best of the Culture stories, but Against a Dark Background best of all.
All of his books are weird, even if not classed as SF, they have fantasy elements. The Bridge is very surreal, the Wasp Factory just very strange.
My favourite of his books has to be Whit - one of the funniest books I've read. I love the curried Haggis and stuff. I really want it to made into a film.
If you like Scotch Whisky read his Raw Spirit.