I watched the movie first many, many years ago. Looking back it's mostly a faithful reproduction of this excellent Chuck Palahniuk novel, albeit not as "schizophrenic". The book mostly reads well. However, whether it was because I'd seen the movie before or not, the "Reveal" wasn't as satisfying as there were a number of suggestive hints throughout the lead-up which seemed to give the game away too early.
One of those rare situations where I enjoyed the film adaptation more than the book. That said, this is recommended reading.