I've read the books and found them very enjoyable.
So is the film.
The budget was low but I think that the director did a pretty good job.
The story is convincing, there's an oppressing anguish that doesn't leave you till the end and that's how an horror movie should be.
I'm not convinced about two things though: first I don't get the role of D. Carradine, not only of the actor but more precisely of the character, it doesn't make very much sense and second the end is a little bit too rushed.
Otherwise I would have rated it 5 stars.