1 star, DNF.
This book wasn't for me, even though I was looking forward to it based on the description. I almost gave up in the first chapter, but kept going thinking things would improve. Fourteen chapters later, that was not the case.
It's too bad, because the world has the potential to be really interesting. However, the complete lack of world-building
turns it into a mess. Terms are dropped without explanation. In fourteen chapters it was never explained why some people are sorcerers and some are mentaths, where their power comes from, or how it works.
The setting is obviously London, but some of the names are slightly changed: Londinium, Themis, Yton, etc. This is highly annoying. Either think up a new setting or use the original names.
All of that could've been forgiven if the book had great characters. Sadly, the characters are meh. After fourteen chapters I still didn't care if any of them lived or died. I was actually kind of hoping for a dramatic death, because that would at least be interesting.
It pains me to quit a book once I've started, but it would've pained me more to keep reading.