I'll preface by saying I really like it, and ask you keep that in mind - because I'm now gonna write a decent bit and a good part of it is about why someone could dislike it.
I am a huge sucker for these types of settings. I goddamn love the character of Filippa, and I feel her actor did her justice. Might just be wishful thinking, but parts of her character design felt inspired by Heather Chandler? Some parts of the source material felt like it worked since there was this 'intentionally-almost-a-parody-but-still-somehow-super-engaging' feel to it. For example some of Filippas dialogue.
Now, a lot of that was changed here, which is certainly for the best. It sounded better this way - the original probably fit better being read. The actor's portrayal of Filippa's anger and violent mannerisms felt real. I think that some parts, like her leaving her dad a voice message about doing good in sports at the school, could feel shoe-horned in to some. Not really to me, though. More things were changed in this adaption. Now, on the one hand some of what was changed took up very little "space" story-wise. On the other hand: changes were sorely needed to make it work in a movie. Like there were no boys allowed in the girls locker after P. E. That would've made it way to unreal for live action - great thing to change. The way they adapted one specific plot point that hinged on this was done competently, I should say.
Some scenes (I won't spoil) felt like they were cool and all, but maybe worsened the pacing? Like they were included since they fit in the original, and those who read the source material would miss them if they weren't included: they made up huge parts of the original's specific thematic style and feel. Thinking of when Josefin shows Alena what she thinks Fabienne and Filippa are really like, for example.
Although I feel that some of the pacing felt disjointed-ish, I still felt for all of the main characters at the end, no doubt. And I personally still love the scenes which some could feel messes with the pacing.
I feel that to a lot of people, imperfect pacing or dialogue which at times 'feels adapted' can get sort of paved-over by a language barrier. So if you're not a swedish-speaker then that might be positive.
On the other hand: being Swedish, some small parts hit extra hard. That's because I know many people that share the characters' 'swedish mannerisms' and use the same choice in wording and intonation, in a way that's kinda unique geographically.
The soundtrack felt fitting, but sometimes I felt it maybe would've been better had it been higher tempo. I'm not a sound guy though, so...
Me personally, I would've liked it if there was more lovin' between the good guys (gals), like in the source material. But I still totally feel that the movie was better as a whole regarding changes made to that. I feel there is a bit of a 'distance' to the story and characters when reading comics which wouldn't have been there in movie format, so the dialogue- and story beat changes were necessary.
It is a movie that people who like this type of setting (an elite boarding school), these types of characters (the upper class bully-girls etc.) and these types of 'supernatural elements' will like a lot. Though I imagine some people might feel that it doen't get deep enough to be as impactful as it could've been - and that it lacks some of the flair the source material certainly didn't lack. Again - I won't spoil, but: deciding to end it the way they did took guts. Worth a watch!
