Went to see this yesterday.
It's weird, way weirder than I expected, almost to the point of absurd in the final act, but I still really liked it.
If you are familiar with the back story of this, it's directed by 21 year old debut director Kane Parsons, who rose to fame making short horror movies when he was 16 on YouTube. The 'Backrooms' series, 'The Oldest View' & 'People Still Live Here' (They're still up online and are a great watch!) before A24 picked him up to take it to the big screen.
If you have watched any of Kane's projects before then you'll know what to expect here, It's a continuation of his series but with a bigger budget. It does stand on its own as a film, so not necessary to know the back story.
A24 seem a really good fit here. For the most part, the horror is in the liminality of the backrooms space and what you can't see lurking around the corner, until the final act.
I saw a couple of young lads walk out halfway through
"Dis is borin, lad" "Ano, lad, nottin's even appennin yeno" (

) so if you go in expecting a jump-scare fest a-la 'Paranormal Activity' or 'Insidious Chapter 15' or wherever they are up to, then you'll be disappointed.
A very solid debut from a very young director.