Here's why I think the book works so effectively (compared to the movie, although the movie gets the "business card" scene down properly). He gets into these rants about 80's culture that are fucking hilarious, mind numbing. Part of the art is to really immerse yourself in what he's talking about when he does a 24 page review of some stupid obscure 80's thing that's totally meaningless, as though it were the most important cultural advance since Birth Control was discovered. Then in the very next breath, he's stabbing a six year old in the throat at a kid's museum, then holding the head of the child in front of the mother as the kid bleeds to death.
Ellis just completely leads you down this primrose path in that numbing way, with the attention to detail both in the endless preparation just to shower and shave, and the way he kills his victims, and chooses them, for that matter.
An unusual read, and in places, just too fucking funny in places...like when Patrick goes into a Kosher deli and tries to order a cheeseburger with a milkshake, and then is totally mystified when the owners get angry at him. Or the way the scene in the movie where he's in the chinese Laundry is written. In the book it's so totally over the top in his head.
Also, watch the video of "The Machinist" it really shows Bale as he should have done Patrick in the movie.