I had a chance to get my hands on a first printing of The Wasp Factory for $20. At that time, I was in graduate school and it seemed like an indulgence I couldn't afford. By the time I talked myself into it, someone had already grabbed it.
If you haven't read anything else by Banks beside TWF or Complicity, you should pick up his new one, The Crow Road, or Whit. They're much more tame but equally engaging.
MB, you should check out O'Brien's 'The Things They Carried.' IMHO, it's one of the best collections of short fiction ever written. It reminds me a lot of Hemingway's 'In Our Time.' It has a lot of the same themes about going to war and coming home from war.