Now, I know French inmates are unlikely to have read Lovecraft (and that proves my point that his writings should be taught in school, maybe as a separate subject), but how did they think something that sounds like "ftagn yog sototh" could possibly lead to any good?

The movie takes place in a prison where four very unlikely cell mates stumble upon a magical book that may, if read right, get them out. As prisons go, the cell was totally unrealistic, so that made it hard for me to get into the atmosphere of things. It also moves rather slowly, which may bore people. But other than that, this is top notch horror feeling, mixing Sartre's "hell is other people" with a Lovecraft/Barker type of story, and doing rather successfully.

Bottom line: take the time to watch this. That means not doing it when you are about to go to work or to sleep or while doing something else. This is a movie that works best if you are immersed into it. Lessons to be learned: Yog is bad, almost as bad as French women.