Librarian here. Chuck Palahniuk describes his own work as transgressional fiction and usually Fight Club is listed as a satirical novel.

While it seems easy to just move books from one section to another ‐ they are actually given specific designations through the Dewey decimal system and the Library of Congress that supply an agreed upon cataloging order and shelving locations.

Link below shows cataloging info for Fight Club.

https://en.m.wikipedia.org/wiki/Fight_Club_(novel)