The Last Exorcism isn't very adventurous in the genre. You can pretty much surmise what happens without watching it. Priest gets a call about a girl that is possessed, its always a girl for some reason. The priest comes, he is usually disillusioned. He preforms an exorcism that pulls the devil out into the real world. In just about every single one of these movies, the person that is possessed is always claiming possession by Lucifer himself. The possession is always dismissed and then returned upon.
This movie was also bitten by the found footage bug that has been haunting horror for sometime now. Thanks Blair Witch Project. The film follows a disillusioned priest that starts preforming exorcisms as a way to show that there is no God. Of course he is proven wrong, just look at the poster for the movie. It doesn't matter. The plot is inconsequential, you are watching this movie to figure out why we are seeing the found footage. Folks. I don't know why you are seeing this. There is no explanation.
The movie just sort of ends, it doesn't offer any explanation and leaves everything up to the viewer. The problem with that is, we are watching to find that stuff out. So, the movie fails. It doesn't pan out the way that they thought it should. Yeah, the movie has a few creeps and creaks. However, the movie doesn't have a good flow. It is very jagged and if you turn away for a few moments, it is hard to pick back up on.
Take this review as a warning. There are better exorcism movies out there. Hell just watch The Exorcist. That movie is shades above this one and both are pretty much the same movie. I started watching this one because Eli Roth attached his name to it. However, maybe he shouldn't have.