The Aeronaut's Windlass

Quite good. Fast paced with lots of action. I am reminded again of how skilled a writer Butcher is. He has created a new fantasy world with physics slightly different from our own and with a unique magic system. This world is inhabited by people both normal and somewhat odd and by an intelligent race of cats, all living in immense “spires”.
Butcher gives only glimpses of the new society he has created. The spire dwellers live far above the dangerous surface of the planet. They depend on a magic-like ethereal technology. There are hints of a robust trade as well as a history of conflict between the spires. Butcher likes to show rather than tell. I expect the society will be fleshed out in subsequent books.
The story features desperate fights in the corridors, rooms, and ports of Spire Albion as the protagonists defend their home from invaders. It also features some awesome airship battles. I feel that Butcher took inspiration from the works of C.S. Forester and Patrick O'Brien.
As you might expect, the story features a variety of characters–the good, the courageous, the cowardly, the bad, the quirky, and at least one that is downright evil. All are interesting (though some are perhaps a bit too genre standard). There is also a glimpse of a dark, malevolent intelligence, which I expect will be more fully developed in subsequent volumes.
Pretty good yarn. I look forward to more.