I found the large majority of American Psycho shocking for the sake of being shocking, and not that entertaining. The film adopts a nicely tongue-in-cheek tone that I did not pick up in the novel.
Upon more recently reading Less Than Zero, one of Bret Easton Ellis' earlier books, I realised what his point was with American Psycho: the frustration and ennui that arises from a 'perfect' life of richness and success, and the need to find something more to entertain oneself, to go beyond more boundaries. This point is very well illustrated in (the much shorter) LTZ, and I would highly recommend it as a partner piece to this. The point is much better put in this book, and this I feel naturally follows on (although very different). Although I've not re-read American Psycho since reading LTZ, I believe the experience would be much enhanced.
I read this in a day, so it obviously gripped me on one level. However, a few weeks later and I couldn't tell you anything much about it - other than all the characters are, I think deliberately, two-dimensional and pretty, and mostly blonde, I think. It wasn't until I finished that I read on the blurb that it was supposed to be a collection of sshort stories. I jjust read it as a pretentiously, disconnected novel!