Overhyped, Overlong, Underachieving, Underhanded Nonsense

Rating: 5/10 (10 June 2018)

This film is not credible, not scary, and not recommended unless you're bored and streaming it at home. Do not waste your money or risk an accident where you or a family member might be decapitated while traveling to or from a theater.
Seriously though, this is a clear case of the hype machine being cynically manipulated to drive box office performance but an utterly forgettable movie.
Stay with me here - I know I haven't even made a single specific complaint about the film, and I will - but Ari Aster can't seem to resist these endings that even MNS might be ashamed of. It kind of worked with "The VVitch" in 2015, but this time it's just too-much-nonsense-icing on top of an already unbelievable cake that failed to rise.
OK enough of the metaphors. The positives: This film is very nicely shot. The lighting is perfect and for about 15 minutes the director does a good job of ratcheting up a somewhat believable tension. The cinematography is great. The acting is just OK in the aggregate - Collette is very good, but I don't even see why Gabriel Byrne signed up for this. The kids have the difficult job of making otherwise ridiculous and totally unbelievable scenarios and behaviors seem as though they might be possible.
Now to the negatives (SPOILERS AHEAD):
People simply do not behave in the ways that are depicted in this movie.
You don't send a 10 year old (I know she was 13 or 14 during filming, but she doesn't look it at all) to a high school party with a senior. A high school senior who plans on smoking some dube doesn't take his 10 year old sister along at his mom's bizarre request without an argument. Further, you don't do that - even if you're grieving-but-not-grieving over your recently departed mother - when the girl suffers from a severe nut allergy and you don't do it without sending an Epi Pen along with your son.
People who just decapitated their sibling in an auto accident don't simply drive home, go to bed, and leave a human head on the ground (much less your own sister's) then wait for their parents to discover the headless body in one of the family's two Volvos the next morning - presumably after bleeding out in the back seat. Additionally, when this kind of thing happens, the cops tend to get involved, amirite? In this movie, however, that's exactly what happens and no police, no cleanup and they're driving the car in the very next scene. Hmmm...
When your son, who has weeks or days earlier killed your daughter, resumes going to school almost immediately, without therapy or counseling, has a seizure and bashes his own face in on the desk, you don't load his lifeless body into the same Volvo, drive him home, and deposit him into his bed - still unconscious - without any kind of medical consultation or observation at all. Laughably ridiculous.
The reaction of the family to the mother's dalliances into the world of seances and such is just not believable. I don't know how else to say it.
And the problem with all of the above is that what little plot there is absolutely requires the audience to suspend disbelief in the very essence of human nature and behavior and accept without any question that these kinds of things are likely or possible.
In addition, the whole convoluted idea is just ridiculous and unnecessary. So the evil, manipulative matriarch wanted to get a suitable male host for her demon lover, but in the process screws up several attempts over a generation, and puts him into a little girl's body instead - meaning that she has to be killed and then he can possess the boy. OMG..SMH...WOW
Finally there's the underlying conceit to the way the whole picture was made. When you have to rely on an unnerving soundtrack to create a mood in a movie like this, you're not doing it right. In any case, it didn't work. At no point was anyone in the audience frightened or unnerved and I heard several laughs and scoffs during moments that apparently were supposed to be scary or meaningful.
I suppose I should have seen this sophistry coming when, prior to the movie, the theater showed an interview with the director who made the ridiculous claim that he views "The Shining" as a comedy movie - and that's it's more effective as such than it is a horror movie. The guy is clearly delusional and making movies only for himself and his industry/film school buddies.
Avoid. I'm not kidding - wait for it to hit Netflix. There are better ways to spend 2 hours.