This would make a good action film in the tradition of Indiana Jones or Lara Croft -- death-defying action scenes on roofs, elaborate machines, dramatic shots like the baddie's empty shoes smoking in a scorch mark after he's struck by lightning. It's got that filmic pacing, too, with the quips coming at just the right moment as if scripted. Although it is cleaner and has more jokes, the movie it reminds me most of is League of Extraordinary Gentlemen, because it has that same facade of Victorianism: the dark, dirty, wet streets of London, the fog, the long black coats -- but no authenticity. Many of the details are anachronistic, and more importantly so are the attitudes and speech. The characters introduce each other by first names, take the Lord's name in vain, have little ingrained sense of class difference. Insofar as one can tell, that is, since we don't get much of what's going on in their heads. They're a bit stock and underdeveloped.
Aside from these criticisms and some plotting weaknesses, it was an entertaining read, imaginative and fast-paced. This was interesting to see in light of the slowness of her adult fiction, which is heavy on description and interior experience. But there are many passages where the sentences ring familiar and her fascination with the urban environment is consistent.