Leviathan begins at the start of World War I, but in a world very different from what we know. The Germans, known as Klankers, have technologically advanced war machines. The Britains, known as Darwinists, fight with genetically engineered war animals. In a genre also known as Steampunk, Westerfeld creates wonderful characters and an original rendering of WWI.
In his series we follow Derryn, a girl disguised as a boy in order to serve in the British Air Service. She soon meets Alek, heir to the throne of a country that no longer wants him to exist. These two characters develop an unlikely friendship as they are drawn into the battles and politics of an alternate World War I.
With an engaging hero and heroine, Leviathan is a great read for all teenagers. It is especially interesting for historical fiction readers to compare actual and alternate histories.