Sadly this book just didn't live up to the promise of the previous two, lacking the evocative descriptions of 19th century London and concentrating on all-out action. It's also not been properly proof-read, or the author doesn't know the difference between "flaunt" and "flout", rendering the motives of several parties nonsensical (why punish someone for flaunting, rather than flouting, the rules?). While it somewhat develops the relationships between the main players, it's lightweight and reads like a rushed job.
On the positive side, as well as the technological staples and 19th century sensibilities of the genre, there is an amusing touch in the form of be-suited, bowler-hatted knights of a Masonic society. However, the truth surrounding Amelia's death was far too predictable from very early in the book. For some reason, I hear Dame Judi Dench's voice speaking all of Queen Victoria's lines!
Hopefully the next volume will have more substance and more atmosphere and a return to the style of the first two books rather than reading like a 350-page formulaic roleplay-spinoff action novel, otherwise I won't be bothering beyond book 4.