In this alternate history of World War I, the German forces [called Clankers] used steam-powered war machines like tanks and the Allied forces [called Darwinists] utilized living creatures as war machines. The Leviathan, for example, was an airship made from a living whale-like creature. Though it looked much like a Zeppelin, it was MUCH cooler because it depended on a complex ecosystem in which the waste-products of smaller organisms [living inside] provided the helium-like substance that made it float. Add that to the fact that people were walking around inside the beast/ship, and it’s not hard to understand why a science geek like me was just as enthralled by the Darwinists’ creations as I was with the whole rest of the story! If you like action and adventure, and you’re not opposed to possibly learning something about world history, this is a book you should probably read. (Just be sure to check out the author’s note in which Westerfeld explains which events/facts were true to history and which he created for the sake of his story.)