It's meant to be funny, I think. There are so many comical things in it, it has to be intended comedy. I'd describe it as a very dark comedy.
With all the lines Patrick Bateman says, and all the gags in it, there's no way they weren't going for comedy. Even the book was like that (I hear). There's too many hilarious lines to quote.
I'm only here to remind Brad to take his protein pills daily.