This is a completely wonderful fantasy adventure, everything you'd want in such a book: it's fun, challenging, thoughtful, exciting, original, enchanting.
It was a burnished, cloudless day with a tug-of-war wind, a fine day for flying. And so Raglan Skein left his body neatly laid out on his bed, its breath as slow as a sea swell, and took to the sky.
How could you resist such a beginning? And what follows doesn't disappoint.
First, it is a completely original world, populated with people such as the Lace, who decorate their teeth with shells and smile when they are distressed. Or there are the Lost, who can leave their bodies and travel, using their senses independently "like snails eyes on stalks." Then there are the Cavalcaste people, the Colonizers, who are aliens, but the ones with power. Gullstruck Island is perhaps loosely New Zealand, but not quite anywhere except itself. Any analogy between Europeans and Maori is not heavy-handed at all and only serves to add depth to the intense and thoughtful story.
The plot centers around Hathin, a Lace girl, and her sister Arilou, who may, or may not, be a Lost. When all the other Lost are mysteriously killed, Hathin and Arilou find themselves fighting for their lives, the focus of a relentless conspiracy. I love the way that Hardinge turns many of the conventions of adventure stories inside out - nothing is quite what you would expect, and everything is complex and subtle, beyond expectations.
It's just a terrific book, and you should read it. What more can I say?