First of all, did Ellison Oswalt (Ethan Hawke), this movie's famous true crime author, read Amityville Horror, ever? Yes, that haunted mansion was all made up, but so is this scary movie universe, which at a baseline fiction level means that they're both exactly the same thing, which further means that an experienced writer about terrible killings should have the common brains not to move his entire family into the murder-house his new book is based on without letting them all know and giving them a moment to consider opting out. He is not only the world's weirdest and least considerate method-writer, he's also blatantly asking a swimming pool-haunting pagan diety named Bughool, who looks like every single guy in the black metal bands Emperor and Immortal, to make life extremely difficult for him.
Just had to get that off my chest. And yes, that's what happens here, of course. Difficulty. Meaning lots of slayings.
Those slayings are repeated over and over again, to mounting creep-effect and palpable dread, via 8mm home movie reels found in the attic and viewed by the increasingly alarmed author (though not so alarmed that he, you know, tells anyone in his family or does anything of substance to save them from what everyone in the audience knows to be their impending doom). The opening credits, simply and frigteningly, feature what's in the trailer and on promotional posters: four people hanged from a backyard tree in horrifying slow motion. And that's the least gruesome of the lot, so prepare to enjoy the escalating sick as anonymous families are ritually murdered, stylishly assigned a calling card symbol that resembles Optimus Prime crossed with a demonic goat, filmed while dying with the evidence stored in innocuously labeled tins, then viewed by our protagonist, who, again, I repeat, does nothing about it except make a kinda-sorta Concern Face.
But that's the joke of horror. Always. The reason you love it. You politely address the screen, "Perhaps you should all move away from the place that makes unexplained night noises and contorts your children into human origami. That might be a good first step." And the people never do. You, in turn, freak out over (and take pleasure in) their demise. And filmmaker Scott Derrickson, finally hitting a kind of stride after The Day the Earth Stood Still and The Exorcism of Emily Rose, likes horror. He likes it so much he lifts bits and pieces here and there from a laundry list of easily spotted reference points, titles that, for your enjoyment's sake, I won't recite here.
And it's clearly appropriation as fan tribute, not mere recycling, because when it counts (seriously, I know you're sick of found footage, but this stuff is gnarly) Derrickson knows how to jolt you and make you afraid to go home alone after the lights come up. He drops silliness into the action from time to time, letting you breathe for a second, right before plunging you back into that house at night where nobody turns on the lights to investigate that thump. He's good at this, Bughool is a monster probably destined for Pinhead-level adoration, and I'd like some more, please. You will, too. Prepare to feel disturbed.