Very solid. I continue to be impressed with 'Mike Truk' and his work. This book is well worth reading even if you don't dig the sexy parts and you want to gloss over them. The story is engaging and the world is very interesting and well crafted. The characters are deep, interesting, and likeable.
If I had to level some criticism, I would (broadly) say two things. The first is that the sex, and by association, the relationships, are not given enough focus or time. The sex scenes often feel rushed, and lacking in detail, they're few and far between, considering the genre, and they tend to be somewhat samey. The author has interesting ideas for them but he doesn't spend enough time or care on them, in my opinion. There's also a shortage of time spent on character interactions-- we don't get to see a lot of characters having meaningful interaction with each other, or building relationships, and this means that when the sex scenes come up, or characters find themselves in peril, we don't really feel the gravity of the situation. This is in stark contrast to the almost-rambling prose that occurs at several points while the author is trying to be evocative in describing the city. To be fair, the city is basically a character in its own right, but there were passages that were repeated almost word for word to try and set the scene for wandering around the city, and they grated a bit. I didn't need to read 'costermongers' that many times, or hear about the coffee stands in three different parts of the book. Too much focus spent on this sort of thing, not enough on the characters and their relationships, in my opinion. The characters are intriguing, give us more of them and spend less of your word-budget repeating yourself!
The other thing I would point out is that the author often seems to forget details, and this is something I noticed in his 'five trials' book as well. There are some points of iffy continuity from scene to scene, and certain elements seem to be forgotten, like they slipped the author's mind (there were a few I noticed while reading, one I can recall off the top of my head, without spoilers, is the body of a certain deceased character that was being carted around for multiple chapters rather than being left behind, which just seemed to disappear between scenes, despite there having been nowhere to put it). These kinds of mistakes are usually minor, but can really knock your head out of a story. The author would benefit from dedicated beta readers to help catch these things.
The author's biggest weakness is overall lack of attention to detail, in my opinion. Forgetting elements of what's going on, and not bothering to be descriptive and detailed with the characters and the intimate scenes is a problem, for this kind of work. All in all, this book is great, though. It's an engaging story, kept me interested up until the last page and hungry for more. It could be much better, but I'm still comfortable rating it 5/5 because while it DOES have flaws, the work is good enough to make all of those flaws forgivable.