A freaky roguelite dungeon crawler with a borderline incomprehensible plot and unexplained game mechanics that require wasting runs to understand. It's novel, at least.

The gameplay is serviceable despite not explaining anything about the systems, the atmosphere is outstanding, and the core loop can get fun if you don't exclusively get bad items or spawn between two enemies. It succeeds at being fun while also being scary, despite some enemies being horribly designed.

The main issue is the story and the lack of any explanations in the game itself.
Usually, I wouldn't mind it, and wouldn't count it as a negative, if it wasn't for the fact that it was a deliberate choice to sell it as separate material and separate novels instead of including the texts as an obtainable "lore" section/item in the game. The integrity of the storytelling is blown to shreds.

I love obscure storytelling that makes me think, I do not enjoy being deprived of already-written content because they wanted me to go read the author's blog about it, and also buy his books and drop by comiket.
If you are the type of person that gets obsessed and digs through archived posts from two decades ago to understand one comment that should've been in the game to begin with, you have plenty to look at here.
But I'm not.
And I'm not going to judge it based off external material written post-release either. And if I had to, the rating would be even lower.

Not that the story or world itself was good either, it's trying too hard and the execution is too flawed to be truly enjoyable. It's just very interesting to look at.

The cutscenes and their execution range from expertly crafted bizarre artpieces to a black screen with text on it for two minutes, most likely due to lack of budget.

Overall, it's fine.
If you don't care about any of the above and play games only for the vibe and gameplay, this is a fun time.