Set during World War I, Behemoth tells a steampunk-esque alternate history. As in real life, the assassination of Archduke Franz Ferdinand triggers the conflict, but in Behemoth, the archduke has a secret heir whose life must be preserved at all costs. That is not the only historical divergence from reality, however not by a long shot. Behemoth features a familiar sociopolitical landscape but radically different scientific one. In this world, the British and other Allies are known as “Darwinists”, as their knowledge of biological sciences is super-advanced, to the point where instead of airplanes, they have giant, living airships (such as the eponymous Behemoth), and instead of something like walkie-talkies, they have messenger lizards. The Germans, meanwhile, are known as the “Clankers”, and they have eschewed the use of the biological creatures in favor of mechanical might; so where the Darwinists might have a giant, living airship, the Clankers would have giant mechs and other mechanical marvels.

Behemoth, the second book in the series (following 2009’s Leviathan), takes the protagonists British midshipman Deryn Sharp, and Prince Alek, heir to the throne of Austria to Constantinople, a city where the Darwinist and Clanker philosophies collide. There, the two are thrust into an explosive political machine that threatens to destroy all they’ve worked for, even as both Darwinist and Clanker factions attempt to sway the Ottoman Empire into joining their side in the conflict.

Every bit as full of a sense of wonder as its predecessor, Behemoth is a thrilling, masterful piece of fiction, a sterling example of what alternate history, steampunk, and speculative fiction is capable of. Peppered with enough details from real history to lend the book a rich authenticity, Westerfeld spins the story in wildly new directions at the same time. Although Behemoth is categorized as a young adult novel, it’s really a must-listen for anyone who enjoys speculative and/or historical fiction no matter their age.

Veteran and highly regarded actor of the stage and screen Alan Cumming’s performance is nothing short of enthralling. His Scottish brogue lightly accents his narration, but disappears or transforms into something else entirely when voicing the dialogue of the Austrian Prince Alek and the German Clankers and the other characters. Likewise, he does an excellent job portraying the teenage Deryn, a girl passing herself off as a boy. Somewhat subdued, without much vocal trickery, Cumming’s narration is simply a pleasure to listen to.

A brilliant book plus brilliant narration equals a surefire contender for audiobook of the year. John Joseph Adams