Dragon's Lair in San Antonio, which has a clearance table with games, comics, and other merchandise marked 75% off the original price.
I don't actually play GURPS (the Generic Universal Role Playing System), but I'm a big fan of the Vorkosigan series of SF novels by Lois McMaster Bujold. So the chance to snag a $40 hardback detailing the setting of those books for ten bucks was one I had to grab. So I did.
The sourcebook from Steve Jackson Games has a lot of background on the novels' locations, characters, technology and history. It also contains a streamlined version of the game called GURPS Lite. I don't think I'll be starting a GURPS campaign anytime soon, but I'm enjoying reading this supplement.
I'm curious, has anyone else ever bought a game product just for the background material?