Leviathan

In an alternate 1914 Europe on the brink of World War I, fifteen-year-old Austrian Prince Aleksandar Ferdinand flees his homeland when the Clanker powers (the Austro-Hungarian and German empires that rely on steam-driven war machines) attempt to take over. He forms an unlikely alliance with Deryn Sharp, a British Darwinist who has disguised herself as a boy to join the British Air Service and is learning to fly aboard the Leviathan, a massive genetically engineered whale airship that serves as the flagship of the British Darwinist fleet. The two protagonists, from opposing sides of the war, must work together as they navigate the conflict between the Clanker powers and the Darwinist nations.