2K and Tor Books have teamed up to publish the first book about the Bioshock-universe. Called Bioshock: Rapture, and written by John Shirley (previously mostly known for his cyberpunk-works, some written together with William Gibson), the book is out in the middle of July in the US (July 19 to be exact) and the story takes place before the events in the first game.
If you want to get a sneak peak, there's an excerpt available on Tor's website.