I don't want to add any spoilers so I won't go into detail, but MAN, there were a handful of "video footage" scenes that were so scary, I haven't been able to wash my face without keeping one eye open while I splash with water, you know what I mean?
For me, the thing that makes it so scary is 1.) it's all so hyper realistic 2.) the characters (some of them) are so vulnerable and authentic and even kind of lovable that the scares have a lot more impact. If you're hoping to see just another popcorn movie where the gang of vapid teenagers gets butchered, this probably ain't the film for you. On the other hand, if you wish they were still making movies as meaningful and scary as Rosemary's Baby, Repulsion, The Shining, Texas Chainsaw, Henry Portrait Of... and even (to mention a newer flick) The Ring, then you absolutely have to check out this new cult classic.