I'm sure that this has already been recommended but I'd like to give my +1, and that goes to American Psycho.
I've not read the book, but the movie is something of a cult classic.
I would also recommend The Room. If your local cinema ever happens to be screening the lamentable masterpiece by Tommy Wiseau then take a group of friends and never look back. One of my favourite movie experiences to date.
I've read the book twice but not seen the film once, but the book is a favourite of mine. I keep meaning to watch the film but never get round to it. Apparently it's not as debauched/explicit which is understandable.
One of my favourite parts from the book:
I even thought the fourth one was pretty decent as I was expecting it to be shit and crap all over the franchise.
Same here, though I don't really consider it as being part of the original trilogy since I don't feel like it fits as much. Jim's wedding was a logical conclusion for the series... At least for me.
I still went to see it in theaters and had a good time, though.
Ditto on all counts. I hope they make another. The characters will never get old to me.