Okay, that was difficult to watch. I hate this movie and most of what it did, and it goes right into the list of my favorites. Masterfully done.
Plot. I didn't know a movie could build up such good empathy for the characters and manipulate you to form a belief that you know and understand the characters, even despite heavy foreshadowing and me being aware of the fact that Lars von Trier is not exactly known for slice-of-life no-thoughts-head-empty easy-watching things, and then completely shatter that belief. Make all the characters do terrible, grotesquely realistic things while giving off the "hmm yeah, it's not like these characters are very unusual" feeling (contrarily, that's what a person in a situation like that, having figured out an opportunity like that, would likely do), aggravating the situation for an hour straight without making it seem like a trying-too-hard heap of tragedies and suffering for the sake of edginess and tear-jerking, and then ending it on a self-contradictory note, with a paradoxical decision by the protagonist and just shrugging off any questions by saying "lol stupid questions, we will not answer".
Characters. This movie really nails the descriptions of different archetypes of people, being quite light at first when the main character attempts to explore and play around with the people's psyches, and then getting darker after various little missteps the heroine makes result (or do they really?) in the other side of the characters around her being revealed. The relationships between various personalities are also very well-written.
Visuals and storytelling. The storytelling was quite unusual, akin to an audiobook or a theater play, with characters' thoughts and actions being narrated rather than shown; to give more weight to the theater similarity, there were also no walls, with only lines on the ground that signify any walls or doors (the actors do convincingly pretend to open and close the imaginary doors, though).
Soundtrack. Was there even any, aside from a song in one scene performed by the characters and the ending credits song by Bowie? I don't think I really noticed much of it, and honestly, that's good, the movie did not need any soundtrack, the silence fit it well enough.
To conclude, I found the movie to be "an experience", and an experience worth going through. It is somewhat hard to recommend a movie like that because of the emotional impact it makes on you, not allowing you to disconnect and not emphasize with the characters, though.