My initial reaction was: not a lot happened until the end, but I was okay with it because the ending was sort of spectacular and also ambiguous and I still haven't drawn any firm conclusions. 
 But then I thought about it and, actually... Quite a bit did happen in the beginning. A lot of it was lost/forgotten in the larger mystery of things. 
 First, the characters: Nathaniel ('Thaniel) Steepleton is a telegraphist and pianist working for the Home Office in Victorian London. 
 Grace Carrow is a woman who sometimes dresses like a man because it's Victorian London and a gal ain't allowed to go in the library, apparently. She enjoys doing science experiments (also not a fitting profession for a woman) and is trying to prove the existence of ether, the substance through which light moves. 
 Keita Mori is London's best watchmaker. He is also an inventor of all kinds of clockwork gadgets, including a sock stealing, lifelike, octopus named Katsu. There is much more to Mori than meets the eye, and his mysteries will keep you guessing even after you've finished the book. Just know that almost everything he does has a reason behind it. 
 So here's the deal because I feel like I need to say something about the plot, but I promise to tell you only the early parts and reveal nothing major: (view spoiler)[On 'Thaniel's birthday, someone breaks into his apartment, cleans his dishes, heats him some water for his tea, and leaves him a beautiful not-working pocket watch for a gift. 'Thaniel doesn't know who it is and the police (IIRC) basically laugh him out of the Yard for complaining that someone broke in to wash his dishes and leave him a gift. So he goes on about his business, all the while wondering what it could mean. Meanwhile, Clan na Gael, a group of extremist Nationalists is blowing stuff up and threatening to bomb every British government building (including the Home Office where 'Thaniel works) about six months from then. After the six month mark, the police become a little more interested in 'Thaniel's watch because it looks like it might share some of the qualities of the bomb's timers. (I know this sounds like a major spoiler but I promise- it's not.) Ultimately, 'Thaniel is recruited to help the investigation. (hide spoiler)] 
 All this serves to set off a much longer and stranger chain of events and bring these characters together. There is not a lot of action in the book save for the end, but the plot is intriguing and the character's are mostly likable or at the least, very interesting, and the book, though slow in some places, was unputdownable. 
 The writing is beautiful and somehow complements Mori's clockwork gadgets wonderfully. It was also very adult, which was a nice change from a lot of the YA fiction I feel like I've read this year. I absolutely loved the setting. Pulley brought 19th century London to life with steam engine trains, cabbies, dark foggy nights, gas lit lamps, rainy weather, and a small Japanese "village" within London (I liken it to Chinatown, but calling it Chinatown feels wrong because it's distinctly Japanese as far as I know). We also get to see Japan, through some of Mori's memories, and I'd like to tell you she also nailed that but honestly I know nothing of 19th century Japan. 
 The ending is ambiguous (to me) and if any of my GR buddies have read or do read this I'd love to hear your thoughts! I'd also recommend anyone interested in reading this, read it as a group or buddy read for that reason. There aren't any life changing revelations here, but there is plenty to be discussed. 
 I wouldn't categorize this book so much as fantasy or sci-fi but historical fiction with some of those elements thrown in. I'd recommend this book to anyone who enjoys character driven books and doesn't mind a slower pace. I would also recommend that you don't read the blurb, because I feel like it contains a major spoiler that may or may not lessen some of the book's intrigue and your enjoyment. 
 Damn I wish I could say more. I feel like I haven't done the book justice. If any of you has questions- I'm happy to answer in spoiler tags so as not to ruin it for anyone else.