If you've read a Priest novel before, you know a good chunk of what you're getting into already.  If you haven't, Priest loves multi-layered plots, deep explorations of psychology, dark backstories, and strong characters that either a) don't fall into the standard bl tropes or b) are determined to break them.
I'm going to be honest, its been about two months since I finished this novel so I don't remember a lot of the details of what Priest was diving into for deeper thematic explorations.  It does come off a bit as a sort of "case of the week" type story, especially as the story's arcs are very clearly broken up by the cases they end up solving but they were all very interesting cases.  Unfortunately, I found the whole revelation of who/what the Silent Reader actually was and the grand mystery tying all of the cases together to be a bit overly convoluted and unnecessary, which is ultimately the main reason that I didn't rate this book a full five stars.
Things I absolutely loved though:
There are layers upon layers to the onion in this story.  This ultimately did harm it in the end but it still made for a pretty good mystery that kept me intrigued until the end
The slow burn relationship between Luo Wenzhou and Fei Du was a lovely balance that helped keep it from getting too dark, especially considering Fei Du's backstory.  It did seem to suddenly rush a bit too fast on Luo Wenzhou's side but I liked how that added an unstable element instead of bringing them together more easily.
Priest has always done a really good job with her supporting characters and this book is no different.  Luo Wenzhou's team of detectives are the main supporting cast and I loved all of them, their inside jokes, and the way they played off from each other.
Fei Du is for sure, the best and most nuanced character in this book and he's incredibly memorable.  Even now, just pondering back on him evokes a whole gamut of emotions in me.