Great movie, bland book.
I'm fairly torn on American Psycho because of its source material and the film adaptation that came from it. The movie is perhaps one of the best dark comedies out there, and provides what I firmly believe is Christian Bale's best acting roles. The cinematography is great, the story rolling in a more cohesive fashion, and it lacks the same level of gorn that made the book a turn off to read through fully.
The plot is the same in both cases, telling of the conservative and wealthy WASP Patrick Bateman in the heart of the eighties. The film and the book both detail the exploits of him and his shallow friends as they go through their daily pretentious lives, and they document Patrick's descent into insanity as he goes through several homicidal bouts of increasing intensity. But as the story goes on and events grow more insane, we're left to call into question what actually did or did not happen?
When it comes to the book and why it feels inferior to the movie that it spawned is that it simply is a chore to read through it. Ellis laces every single paragraph he writes with far too much description, and it seems that every sentence has at least one brand-name mentioned. And yes I know it's there for thematic reasons on consumerism and blah blah blah, but by the end of the third chapter the novelty has worn off. Yes Bret, we get it, very subtle. And as I mentioned, the gorn is absurd in its description. I'm usually not that squeamish, but some of the violent scenes in the novel are just... ugh.
So yeah. I'm not sayig you should avoid the book entirely, but the movie does make for a more entertaining experience.