It was interesting to read this book so soon after reading What Moves the Dead. I can see why Ursula Vernon wrote about it in her afterword as being a similar setup and recommended that everybody go read it immediately.

The book itself is immensely creepy and I found it very compelling. The plot setup is that socialite Noemí is asked by her powerful father to go investigate what's going on with her cousin Catalina's marriage in an isolated rural mansion. The creepy atmosphere is spectacularly well done: a decrepit remote mansion, very little electricity, locked windows, strange dreams, family secrets, suspicious local history, the overly strict housekeeper with too many rules (silence! no hot baths! no coffee!), also the household's obsession with eugenics and "superior races".

The book's pacing was excellent for me. There is a slow build of mystery and unexplainable occurrences. Backstory is slowly revealed, but there's more questions than answers and Noemí is not sure she can even trust her own experience. And then, suddenly, there's a gut punch reveal and the action shifts, leading into the climax of the book. The mystery reveal felt exceedingly well-crafted to me; rather than cheapening the spooky atmosphere, if anything everything got even creepier once the mask was off, and it fully justified all of the atmospheric details that led up to that point.