Fight Club is written by Jim Uhls with a little bit of uncredited help from his friends Cameron Crowe (Almost Famous) and Andrew Kevin Walker, who worked with David Fincher and Brad Pitt on Se7en.
Jim Uhls was born in Missouri, which isn't exactly a hotbed of fighting and corporate greed, but he was still selected to write Fight Club, his very first feature film, after fighting (not clubbing) to keep all the voice-over narration in the film. Chuck Palahniuk's novel is very heady, internal stuff, so we can't imagine the movie without it. Good call, Uhls.
Maybe Jim Uhls joined a fight club and disappeared after writing this movie, his first, because he's only credited (via IMDb) on four more movies over the next ten years: Semper Fi, Sweet Talk, Jumper, and a short film called Money.
He still gives advice to screenwriters, though…and sometimes he tweets.