I'd only read one of this author's books previously, but The Alchemy of Stone had been recommended to me by a couple of people, so when I was able to pick up a second-hand copy quite cheaply I decided to go for it.
The main character, Mattie, is an automaton who lives in a city which is run by a Duke with assistance from two factions - the Mechanics and the Alchemists - who both think what they do is more important than everyone else. Mattie was made by one of the Mechanics but is self-aware and has gone into business herself as an Alchemist, though her creator still controls her more than she is comfortable with. She exists in a kind of legal limbo, not human and not automaton, which allows her to be places and be overlooked but also leaves her with a massive amount of uncertainty.
As we visit the city where Mattie lives, things are starting to fall apart. This is a city which was created by gargoyles, who manipulated the stone into the shapes its original inhabitants wanted but who are now getting bored of being effectively immortal. Because of Mattie's outsider status, they approach her and make a request: can she find a way of making them mortal again? Alongside this, the activities of the Mechanics in particular are starting to have serious consequences for everyone in the city, as their machinery begins to replace human beings and also be used to control them more and more.
Mattie gets involved with the fringes of a revolutionary movement, though she doesn't initially recognise it as such, while her burgeoning relationships with human beings continue to fall down over their inability to look past her outward appearance. Her creator in particular has a powerful and extremely creepy hold on her, not just retaining the literal key to her heart (without the use of which Mattie can't continue to function) but also feeling free to remove or adapt parts of her body without permission.
The Alchemy of Stone is a beautifully written book and the setting in particular is extremely atmospheric - Mattie's situation, neither human nor mindless automaton, is well delineated without becoming self-pitying and most of the supporting characters are also well-drawn. Where it falls down a little, I think, is the abruptness of the ending. As I was getting towards the end, I found myself looking at how few pages were left and wondering what would remain unresolved, to which the answer is 'quite a lot, really'. If you can tolerate that, this book might be something you want to get hold of.