Great plot twists. Very intelligent. Everything plausible. Things very hard to find in a movie these days. I'm not a psychologist but I felt like the way the therapy session developed had a very authentic feel but at the same time was exciting and interesting. It's a stark contrast with the average movie today that appears to target a 14 yr old audience.
People say that it's very gruesome and it does have some parts but much less than other movies,and it's only a few short scenes.
I don't usually like thrillers but it's because most are garbage and have huge flaws. Thrillers like this I could watch on a regular basis. The ending in particular was very good but there wasn't really a dull moment.