Chuck's work is usually labeled as transgressional fiction, where characters who feel confined by the norms and expectations of society and who break free of those confines in unusual and/or illicit ways. There is always a great amount of social satire in his writing as well. I also feel many of his novels are grounded in elements of horror.
In Fight Club has the very essence of body horror. Guys square off and beat the hell out of each other. Their bodies get mutilated with brutality inflicted upon one another. Without giving anything away, there's also a lot of psychological horror involved in the tale.
In Lullabye the tale surrounds a reporter investigating SIDS. He discovers the culprit is an African poem from a book. He falls under the spells power, using for his own personal gains.
In Haunted A group of people answer an add for a writer's retreat. They get locked in an old movie theater for three months and are told they will not be let out until each has finished a story. The organizer then starts to manipulate the situation by cutting off food, power, ect. The novel contains three sections in chapter: a story chapter, a poem about a particular writer on the tour and a story written by that writer.
In Diary a woman finds her husband in a coma. She was once a promising art student who now lives an the island of husband child hood. Suddenly she gets the urge to begin to compulsively paint. She finds out she is part of a conspiracy that happens on the island.
There are also some horrific parts and scenes in his novels Survivor, Invisible Monsters, and Rant.
For more of Chuck Palahnuik, go to his website The Cult