Leviathan
This steampunk alternate WWI history makes a great family road trip book (Alan Cumming narrates the audiobook). Aleksandar is a Clanker, part of the Austro-Hungarian force of steam-driven machines and guns. Deryn is a Darwinist, part of the British force of genetically modified animals, including the Leviathan, a whale airship. When they cross paths, the two foes develop an unlikely friendship and travel the world on the adventure of a lifetime.
Publisher’s description:
Prince Aleksander, would be heir to the Austro-Hungarian throne, is on the run. Deryn Sharp is a commoner, disguised as a boy in the British Air Service. With World War I brewing, Alek and Deryn’s paths cross in the most unexpected way–taking them on a fantastical, around-the-world adventure that will change both their lives.