The addition of Gonzalo, who relies on Senor X to help him navigate the world, and the enigmatic Martine are good ones, and seeing the league at work in its entirety is interesting. While there were a few moments when I thought that they would dispatch Philomena and the book would be over, and I was disappointed that she managed to somehow disappear, this certainly added to the dramatic tension and made me cheer when she was finally neutralized.
Archie's self doubt and reluctance to fight were an interesting twist, but given his origin, completely understandable. He adds depth to a novel that otherwise would have been a much simpler exercise in bashing monsters.
Readers of Westerfeld's Behemouth, Ross' The Fog Diver and Oppel's Airborn will enjoy this alternative look at 1800's America with its Steampunk machines, multicultural characters, and plenty of sound effects.