One of the BEST psychological thrillers to come out for years. Olson acts the fuck out of this, the editing is smart and the script horrifying. The ending will keep you feeling on edge for days... Also, if you like this, I recommend Tom at the Farm (Dolan, 2013).
While it is certainly a good movie, the only character that stands out is Martha. Her sister and the husband are more standard representatives of American modern society than they are real people. The man works, the woman is at home doing chores and sometimes friends come over for a party. So while the story of a girl adapting to society worked, I would've liked the sister and the husband being humans as well.
The comparison here between upper-class suburban life to a cult may be an interesting one, as both groups are about assimilation and following what you are told, unless of course you don't fit in, try to break free, or are not accepted. While the acting is good, the characters feel less like people, and more like a plot device for that message. Ultimately, the narrative is more repetitive and gimmicky than weighty.
Slightly weaker upon a second viewing. Sean Durkin's debut is an uncomfortable and hazy dive into the underbelly of American mythology via the life and recollections of its confused, enigmatic protagonist. Its easy to get lost in its elaborate and associative structure the first time around, but a revisit reveals traces of constructed ambiguity and philosophical indifference. What is the director trying to tell us?