What can be said about this?
It's a piece of artwork.
Too often films are made with pleasing the audience in mind, this one doesn't. It goes further into the dark recesses of your mind than any other film I've seen. This one gives you an insight into a very disturbed person.
Instead of the main character being some kind of hero or good guy, this one has a psychopath with a very disturbed mind.
I couldn't think of a better actor to play the part of Jack than Matt Dillon who portrays him brilliantly, even on a par with Jack Nicholson in The Shining when it comes to putting across his level of insanity, with excellent results.
It's easy to see why film critics gave it bad reviews, they wouldn't want to be seen giving what is basically a brilliant film like this a good review for fear of being called disturbed themselves.
If you like dark and disturbing, I highly recommend it.