If you haven't read the book, then this is a pretty good stand alone bog standard horror. It's creepy and original in parts but sadly, it captures none of the desolation and gothic pagan horror of the book.
Worst of all, the great twist at the end of the novel has been completely left out here, which is a massive let down.
If you've read the book, then you'll most likely be disappointed with this effort. Apart from the fact that it's not set in England in seedy bedsit land, with the whole seedy prostitution thing and unremitting hopelessness, but is taken to America (yawn) and pumped so full of Hollywood botox all the character and desolate horror is wiped clean out of it.
Shame. But then predictable. I'm hoping they remake it with a British production that captures all the mood and atmosphere of the novel.
If you didn't like the movie, go read the book. It's one of the best horror novels I've read.