In an alternate-reality early 20th century, Alek's parents are murdered, kicking off a war between the Clankers, who possess highly-advanced war machines, and the Darwinists, who have unlocked DNA and the key to manipulating it to engineer animals and ecosystems to their purposes. He is forced into hiding as the center of a history-changing secret. At the same time, Deryn Sharp begins her career as a middy in the air service for England (a Darwinist ally) masquerading as a boy on a giant living airship, the Leviathan.

I liked both of the main characters in this book, but I loved Deryn especially. Her parts of the book flew by. It was a great beginning to a story, and there will be more, but I was left unsatisfied by the ending in this one. It just didn't feel like the end. Obviously, I look forward to the next book and finding out what happens next.