I have a lot of feelings about this book! My first reaction was that I'm not entirely sure what that was, but it was beautiful. 
 Having now had over a week of digesting it (and rereading bits and pieces, sometimes more than once) I'm going to try and write a proper review. The first thing to say is that I found this book completely defies categorisation. If it's anything, it's fantasy (adult, not YA) but there's aspects of it that read almost steampunk-like, but then maybe it's more of a historical novel with bits of magical realism thrown in, or maybe it's even a romance in some form... 
 I found it a bit slow to start, and for a while I wondered if I was going to get into it at all. But once I got used to the pace, the slow build up and unfolding of the story and, most importantly, the relationships between the characters worked really well. All of them were such complex individuals, and the way their paths gradually crossed and intertwined and they slowly revealed parts of themselves was really beautifully done, and at times almost painfully sad. Thaniel and Mori's relationship in particular was so delightful, developing subtly bit by bit until where it ended up was somehow inevitable. 
 The plot - the bombing of Scotland Yard and who was responsible - was just as intricately put together and was more of an undercurrent to the character-driven aspects but flavoured every part of the story, the interactions between Thaniel and other characters, Grace's distrust of Mori, and added a layer of tension. I loved the way that for a long while you were never really sure who to trust, who was on whose side, what was truth and what was lies. 
 The climax related more the character arcs and relationships than the bombings, and while it was confusing I didn't mind that because it reflected the characters' confusion and the fact that for once Mori couldn't see what was happening. I didn't like Grace as much as the other main characters, but her turn didn't feel overly dramatic because I could feel her panic at the way things were going, and her frustration that Thaniel didn't feel the same concern. Her reliance on logic to try and resolve what she saw as a threat was entirely in character and it led to a better conclusion than the one I initially thought we had been heading to. 
 Also, the hints dropped throughout the book added so much depth on the reread!