It is mentally disturbing, not just blatant sensationalism. Nothing that goes on visually is all that bad (though there is a rape scene, among other things) but the story line will get to you if you can follow it. Definitely worth watching and pretty true to the book.
I read the book first, then saw the movie, and I wasn't disappointed in either. I must say, though, that I haven't repeated either experience, and I usually re-read books that I find truly worthwhile.