Eli Roth has a lot to answer for. "Hostel" (both 1 and 2) are simple horrid shit. That they are well made horrid shit makes them that much worse. I definitely felt the need for a hot shower after the first and wouldn't even finish the second. It's porn for nihilists.
On the other hand, Eli did a good job in "Inglorious Bastards," and "Cabin Fever," is actually a good horror film. Now I see he helped produced "The Last Exorcism." I just had to watch it to see which side of Eli's ledger it falls on.
It's indy shakey cam ville from Blair from the get go. A documentary crew is following a preacher during an exorcism. He's brought the crew because he wants to come clean. He doesn't want any more hustlers scamming people, so he's going to show how the scam works.
Things don't go well from the beginning. The family obviously has deep issues. But they go on and do the exorcism with maximum theatricality. You won't be surprised to learn the exorcism doesn't go well, and the scammer learns there are real demons.
Overall a good film though I don't like the Blaire style. The actors do an excellent job selling the film. It definitely edges toward taboo subjects. A scary little film that helps put Eli on the good side of the ledger.