In a way obvious satire of the greed and ruthlessness of the Wall Street shuffle c. 1990, American Psycho sits firmly in Ellis' own tradition of writing about vapid characters where surface is everything and identity is pretty much meaningless. It's infamous for its violent scenes and famous for the redundant description of things as well as music 'reviews' which these days would have been written by AI. 
Whether the murders 'really' take place, Word of God (i.e. BEE) is that they do, although some of the crimes including the car chase are more than a little farfetched..
It's hip to be square ....