I just came back from seeing this at the theatre, and am reeling. This movie is unbelievably taut. Not a frame feels wasted, and it transitions into becoming a horror movie perfectly.  I think I'll need to see the movie again to unpack it more. Felt there is quite a lot to chew on. 
I'm just joining the chorus of voices here saying this movie is unbelievable....but man.....it is extremely good.   It's probably because it was opening weekend but man, the audience at my theatre was a BLAST to watch this movie with. First movie in a while that reminded me why I love going to the theatre/how seeing a movie with a public audience can really enhance the experience.