While it seems weird and sometimes while you are watching this you may forget about it, the movie is shot in "Found Footage" kind of style. But let's start from the beginning. A very disturbing beginning that had me chilled. Not because of a loud noise or something big happening, but the creepiness of what was shown on screen.
The goal of the movie is to creep you out and it does a very good job. Even if you don't like the themes (or the acting for example), you can't fault the technical aspects of the movie. Someone really thought through what they were going to do. Even so, you might be confused and irritated and might not like what you see. But the movie does not aim for liking it as I already stated above.
It might be slow most of the time, but the mood it creates makes up for that. It's sadistic to say the least and tough to watch. Creatively speaking I was more than surprised what I got to see. There's nudity and intercourse, but it's not about those things. It's about detachment and losing ones mind ... portrayed in an excellent way.