Goliath is the third and final book of the Leviathan trilogy by Scott Westerfeld, which follows the adventures of Deryn Sharp and Prince Aleksander of Hohenburg (Alek). Deryn is a midshipman on the British airbeast Leviathan, a girl who has disguised herself as a man, calling herself 'Dylan.' Alek is the son of Archduke Franz Ferdinand, the heir to Austria, whose murder helped start the first World War. In this world, rather than technology progressing as it does today, there are two camps of different technology. On one hand, the Darwinists have taken to genetically engineering species into a vast variety of uses, and on the other, the Clankers use steam powered machines.
Spoiler-free introduction out of the way, this book continues to tell the story of Deryn and Alek's journey on the Leviathan. Having just left the Ottoman Empire, they continue East into Russia to find Nikola Tesla, who claims he has a solution to the war. Also, Alek learns Deryn's biggest secret. Neither of which are spoilers if you read the jacket summary. But anyways. I love Alek and Deryn, and I think this may have been my favorite book of the series, as they come to really understand each other. All of the storylines planted in the earlier books come together, and while I think the ending went unnecessarily far, you always kind of knew there would be a happily ever after. And yeah, I'm a sucker for those when they are deserved, and both Deryn and Alek went through a lot through the course of the books for the sake of their people, their secrets, and each other.