** WARNING - SPOILER **
The story begins as Yagharek the Garuda arrives in New Crobuzon desperate for someone to restore his lost ability to fly. Garuda have wings, and his have been sawn off in judgement for his crime of "Second degree choice theft without respect". Isaac Dan der Grimnebulin, a renegade scientist, takes on the commission of restoring his ability to fly, and comes almost to the point of being able to fulfill it, when the person whose choice had been stolen by Yagharek arrives and requests that he refrain. Yagharek is guilty of a crime, has been judged by his community, and is now suffering the consequences. It is not Isaac's place to undo the punishment. It turns out that Yag's crime was what we would term rape, although the Garuda insists that to think of his crime as rape, and herself as a victim is to horribly misunderstand the situation - her choice to not have sex with Yagharek, and to avoid dealing with the repercussions of it has been stolen, in a manner which particularly disrespected her and their whole community. I *really* like this rephrasing of rape as the freedom of choice being stolen. This throws Isaac into a horrible situation - he has already accepted the commission, and in the process of completing it has become quite close with Yagharek, but if he completes his work and Yag is allowed to fly, he is basically judging Yag not-guilty, and if he refuses, he is judging Yag as being guilty. At least this is what it comes down to in the book. Or at least, that's what it comes down to in Isaac's mind. Immediately following we get a description of exactly what happened to Yag, and honestly I do think he's been punished enough - but I guess the point is that his society doesn't feel that he will be sufficiently punished if flight is returned to him.
I do love this story, even though it is essentially a tragedy. Isaac accidentally releases an enormous threat to the city of New Crobuzon, and is then forced to deal with it. While many others attempt to deal with the slake-moths, it is clear that none of them will be successful. At least not for a while, and the one who has the best chance in fact wants to recapture the slake-moths and maintain them in captivity which we've already seen isn't foolproof. The things Isaac and his friends go through in order to kill the slake-moths and rescue the city are horrible, ugly, and terrifying. The final battle where they manage to kill most of the moths, they also have to fight off the city militia who should be on their side, but who don't have a clue what's going on and aren't prepared to listen. Finally, once all the moths are dead and the battle is over, even the reward of being able to complete his crisis engine and let Yag fly is taken away by the horrible moral dilemma involved. No one comes out of this in one piece. There is no reward for a job well done. Every single thing Isaac loved or valued is gone, and he is forced to leave the city he loves (and saved!) in order to survive. Yet somehow the ending fits. It isn't horrible and depressing. Isaac has accomplished something phenomenal, and at least *he* knows it, even if no one else does. You don't save the world just for the acclamation - you save the world because it needs saving, even though it costs you everything. This ending is bleak, but beautiful at the same time.
Aside from the depressing and realistic bits (which are totally awesome, don't get me wrong) this book is full of totally fabulous characters and ideas and things. Different ways of being and thinking. Ideas about what it means to be human, or sentient, or good, or evil. Having a truly brilliant mad scientist as a main character is lots of fun. The Weaver is a wonderful character, although horribly confusing (but at least as confusing to the other characters as to the reader). The handlingers are fascinating...in fact all of the non-human residents of New Crobuzon are completely awesome. The world is gritty, ugly, and stunningly beautiful all at once.