I have heard many mixed reviews for this book particularly which is why I was initially a bit scared of it. However, I think reading it was definitely no mistake!
Moreno-Garcia created such an incredible book with such a beautifully scary story that showed how Horror does not always have to be the most gruesome or the most graphic. I think what made this particular experience of Horror unique was how atmospheric the whole book was. Every single detail, from the type in which it is written to the way it was told just played perfectly into the overall atmosphere.
While reading this I lost myself inside the halls of High Plance and could no longer acquire my sense of time. It was as if I myself experienced Noémis journey through the treacherous house and its family affairs. The atmosphere gave me chills and I loved it so much! There is just something about this book that made me go crazy about everything going on! 
This definitely gave me Lovecraft and Poe vibes and I am a sucker for that! 
The characters were so interesting, too. The way the Noémi developed during this story was very interesting s she went from sceptic to accepting what is going on! I loved it! The dynamic between the characters and the way they acted with each other was so believable and I noticed myself being wary of characters I thought I sympathised with. 
However, I have to admit that I also have some not so happy thoughts about this. The initial build-up was sow, almost so slow I felt bored. And after cthinking about it for some days, I didn't really feel the ending. Don't get me wrong the ending was good, but I kind of expected something else.
Anyways, I really recommend this for everyone loving horror. I advise to check a more worked out list of content warnings beforehand because this could really trigger some people.