This is a very hard book to rate. As an early example and inspiration of the steampunk movement, it's a highly recommended read if your interests lie that way. As an alternate history of Victorian London, it's reasonably interesting also; the book is based around the premise that when Charles Babbage thought up the Difference Engine it was actually built at the time, and changed the world so that the England in this novel is now running on steam-based computers ("difference engines") and the entire course of technology is changed. However, as an actual novel to read enjoy without a particular interest in either steampunk origins or alternate histories of England, and without the inclination to look up all the references to the historical figures and computing theorems mentioned, it's pretty dry and at times confusing. This is definitely a novel that requires some work to fully appreciate. I have enough background in English history and computing history that I caught a lot of the references without having to do extra research, but I'm sure there's plenty of nuance I missed, and I think the average reader would miss a lot more. If you're reading it without that background and without the interest in looking it up, I don't think you'd enjoy the story alone.

The story is split into three parts, whose characters abruptly vanish mid novel as the entire narrative changes. And while we do meet some of them again at the very end, there are huge gaps in the narrative and many things left unexplained and untold. I found that every time I was getting interested in a character, they'd disappear, probably never to be heard from again as the narrative shifted to some entirely different people and plots. The last of the three parts was the least interesting to me, as I didn't find Oliphant as interesting as either Sybil or Mallory, and it seemed the most disjointed. I was listening to this as an audiobook and I'm pretty sure I listened to Oliphant's section of the book at least 6 times before having any idea how the book ended because I fell asleep every time. The very end of the book is just a series of scattered excerpts, reports, and news articles around events throughout the book that gives some slight closure to some of the plot gaps but doesn't feel satisfying. So overall, pretty mixed feelings about this book.