I think the criticism in the comments are a bit harsh. While it is certainly dull at points, I did find myself thinking about the characters and if they could have done it, which is what you're looking for in this kind of movie. Even all the way up to the end, I wasn't sure, and then things went crazy. It's gonna be boring if you passively watch it without your brain. But if you use your mind as though you're the detective you will be entertained.

I think what hurts it the most is the fact that it does seem quite true to life. Nothing peculiar happens while our lead man investigates the family. There's a few developments besides the typical "where were you last nights" but they don't drastically do anything besides make you think slightly more than you have (if you've been paying attention).

So ultimately I think many people would like this movie if they go in with an open (yet willing to be active) mind.