You know a movie is effective when you just sit through the credits trying process your emotions and get your state back to some form of normalcy.
I knew nothing about this going into it, so I prefer to say nothing that can influence how you feel watching it. I think the experience of this film is much more rewarding going into it blindly. What I will say is that in knowing nothing about it beforehand, there are so many things that run through your mind while watching it. The suspense-filled uncertainty gives you so much anxiety. However, it is not a complicated film at all. In fact, it's a very simple plot, and you can probably figure it out about halfway into it.
But by the end, none of all that matters. I've never had a film make me feel both a cathartic release AND simultaneously feel to take a shower afterwards or do something to move on from the effect of the film. Those contrasts of patient dread and guilty catharsis are something else, and the many successful allegorical references made by the film are just the cherries on top.