Disclaimer: eARC review for NetGalley.
This was a hard-to-categorize read - and that's not a bad thing. It's challenging; much of the central mystery and the mechanics of the magic that does crop up isn't explained until very late in the story, so there's high tension, but also a good amount of confusion to start with. I found the initial pages fascinating and almost dizzying; I couldn't really follow what was going on, but there was enough there for me to keep trying.
It's classified as Urban Fantasy, but I'm more familiar with the YA romance variant, and this is not at all like that. It's more like a gritty crime thriller, with underworld crime bosses, a dingy, dreary and dangerous end of London, and horrifically unnatural monsters/demons committing graphic murders. This is adult fiction in multiple senses of the word; explicit, violent, with deliberately transgressive sex and language that intensifies the violence (it's not erotica; sexual scenes are brief and hopefully not titillating). If anything, it feels closer to noir film tradition, with a side of paranormal horror. It also bears some resemblance to the Jonathan Norris & Mr. Strange style of adult fantasy. Magic or paranormal aren't particularly beautiful, alluring or empowering, but they're there, they're real, and they're taking lives.
It's not a genre or style that I would generally choose to read, given just how dark it is, but it's a very well executed book, a fascinating departure from anything I've come across in the past, and a wonderful genre-defying piece of entertainment for fans of grittier media. I'd give it about a 3.5/5 for personal entertainment, 4.5/5 for quality and execution.