My feelings are a bit mixed about this book. On the one hand, I really like the worldbuilding; the steampunk elements are well-integrated into the Victorian world and are very interesting. I also appreciate the Steam Kings, how they have divided London into area of influence between themselves and how they control people and English politics. We really see the social, politics, economics and technological consequence of the integration of those steampunk elements, a thing that is not generally done but that really help the reader imagining it and also in making this world credible. Besides the characters are well-written and have a strong potential. 
 On the other hand, I had difficulties getting into the story. I think that it is principally because the POV changes between several characters almost with each chapter. It's good that we have a chance to learn more about each characters, their actions and motivations, but because of that, the story is very slow to begin after the initial murder, as we have to learn first about each character's part in the plot behind it. In addition, because we know almost all the characters' motivations but they themselves don't, it is a bit annoying and frustrating to see them struggle to understand what is happening and I wasn't really involve in the investigation. 
 Generally I have problem with seeing authors using popular characters such as Sherlock Holmes, because I always find something unconvincing in their portrayal, they act out of character IMO,... Here however, I had no major problem. Yet I was a bit disappointed that once Sherlock Holmes arrives, the heroines fades into the background. Even if it's logical that he is more talented than her in resolving investigations, I would have prefer that the heroine's part would have been more important. 
 It took me an unusual long time to finish this book, but I'm glad I did as I end up really appreciating it. I would recommend all fans of steampunk to give it a try.