It's one of those books you want to read all over after finishing it because I'm sure the author hid some things I missed in my first read-through.
The writing/prose is amazing, really love the bits and pieces of German which makes is truly unique. The worldbuilding is positively insane.
I wish there was a spin-off that would dive deeper into the history of the crawl space, or Rachel's and Ben's previous jobs/adventures.