I thought this was the Martha Wells book that I've been looking for for years, so I borrowed it from Maggie while helping them move. Now I'm pretty sure that I've read this one before (though not totally sure), and that the one that I've been looking for is actually The Element of Fire.

It's pretty good. The setting is cool: it has the feel of a magical Victorian Europe, with lots of little details about dress and manners to add verisimilitude. Oddly, the characters have the feel of a party in an RPG: very different characters, each with a suspiciously useful skill-set, thrown together with a flimsy rationale. One wonders if it was inspired by a Castle Falkenstein campaign or some such.

I'm looking forward to Wells's new books in the same world.