Not what it appears to be... I really did not-see this coming...
This is one of those horror movies that is actually really deep and symbolical and works on multiple levels and has multiple stories hidden within the surface narrative and in this case it's actually 3 stories that are told at the same time, though only the surface narrative is picked up consciously, the other 2 are picked up subconsciously and that's what makes it disturbing.
Be sure to watch the extended cut, because only there does it really become apparent what the other 2 stories are about. So, here go the spoilers, cause now I am gonna say what I believe those 3 themes are. Obviously on the surface it's a horror movie, but beneath that it's a drama about relationships and about breaking up - some people pick up on that first hidden theme/narrative and so they find it boring because they expected a horror movie, but what they get is an emotional drama.
But no one has consciously picked up on the 3rd narrative - or at least I have never seen anyone mention it - even though it's very obvious when you watch the extended cut. The third genre of movies is that it's a movie about the 3rd Reich and related National Socialist propaganda, ideology and atrocities committed and that's the aspect everyone only picks up subconsciously and that makes everyone feel uncomfortable watching this movie, but without really knowing why.
Which also explains some of the criticism, such as Swedes and Pagans complaining that their culture and ideology isn't portrayed accurately. Of course it isn't, because that's not the culture or ideology it's trying to portray! So the 4th and ultimate genre is that it's really a biting political satire that uses all the other genres as cover.
It's like the travel movies that the Soviet Union published that make the Soviet Union look like some kind of socialist Disneyland. And as long as you were a tourist who was willing to only go to the places he was told to go and to just gloss over all the labor camps and atrocities, it kinda was! And so what those movies were for socialism, this movie is for National Socialism - a sorta satirical video travel guide into a promised National Socialist fantasy land and Utopian paradise that never existed and that only a complete psychopath could ever try to propagate as something desirable.