There is lot of stuff happening in the movie,so its complex and keeps you on the edge once the momentum is built,the movie picks up pace slowly,it can be tedious for some and will may leave some people bored but if you are looking closely and been on the hype train regarding this movie you will continue watching,so after the movie pickups then the chaos starts and after that movie keeps you edge until it ends.
Its a psychological horror which plays with your mind so expect any jump scares,but it will not fall short to spook you,it will leave you thinking for a while.