What do you think of the American Psycho book?

I have read the book a few times, and it is truly an amazing book. But I am still wondering whether Patrick Bateman did kill Paul Owen, and who he did or didn't kill. I understand the themes and the ending perfectly, but I want to know what you people think actually happened. Or if you think that Bret Easton Ellis specifically left enough clues for the reader to make it his/her own interpretation of it.