Fight Club is, on balance, inferior to its film adaptation. To be fair, it's Palahniuk's first novel and probably not the screenwriter's first movie, but it is a story that seems to work better, in many ways, on film. Like most popular fiction--indeed, like most American thought--it's performed (written) with media models in mind, so the postmodern medium of film seems a more natural home for this material than the pre-modern novel. The movie was also a more intelligent and self-conscious work, was more surprising overall, and, not least, had a much stronger ending. (C.P. leaves some questions unanswered, such as: How did the narrator escape from that bus in a late chapter [or did he?]). The movie also, mercifully, doesn't emphasize the book's Christian parable theme, which suggests that the fight club is a form of left-hand Christianity, sinning to attract the attention of God. This is a very silly, transparently juvenile theme which the author himself ultimately ironizes in the heaven/nuthouse of the last chapter.
One thing this novel, along with Colson Whitehead's The Intuitionist, does suggest to me is the efficacy of building a fiction around a constructed metaphor that is symbolically rich (the fight club and Project Mayhem; elevator inspectors). A novel built around such an idea can be a very effective satirical novel of ideas. Thinking up such a symbol is the most deeply imaginative part of writing, perhaps the hardest mental work a writer does.