Scott Westerfeld's Leviathan saga has many elements dear to our hearts, including alternate-history, plucky heroes of both genders, and strange inventions. But after reading the second book, Behemoth, we realized we really love these books for the pure escapist rush.
Minor spoilers ahead...
For those who missed the first book, the Leviathan trilogy is set in an alternate World War I where a number of things are different. For one thing, the British and their allies ("the Darwinists") have developed a kind of genetic engineering, allowing them to create airships and sea monsters (among other things) that fight on their side. Meanwhile, the Germans and their friends ("the Clankers") have created superior robots and war machines.
There are two protagonists: Aleksander ("Alek"), who's fleeing the assassination of his parents and may be the heir to the throne of Austria-Hungary. And Deryn, a young girl who disguises herself as a boy ("Dylan") to become a midshipman aboard the Leviathan, a huge living airship. (Deryn gets to serve aboard the Leviathan thanks to a complicated chain of circumstances in the first book, too lengthy to go into.)
There's a lot of darkness in the two main characters' backstory. Alek's parents are murdered and he's forced to grow up fast and make some tough choices. Deryn's father has died in a balloon accident, which has left her somewhat traumatized. Plus it takes place against the backdrop of one of the most vicious, bloody wars in human history. But what's even clearer in the second book than in the first is that this is primarily a fun, light-hearted — even goofy — series. Unlike, say, the Hunger Games books, which have moments of playfulness and some improbable events, but are fundamentally dark and disturbing.
I guess there's something inherently escapist about identifying with a prince in hiding, who may be one of the most important people in the world and also happens to be both clever and dashing. Or with a girl who manages to turn herself into the most gallant midshipman in the Navy, and goes around being more competent than everybody else, while still managing to be wide-eyed and spout the endearing catch-phrase, "Barking spiders." But you won't believe how much you'll want to be either one of these characters by the end of the second book.
With Behemoth, Westerfeld takes the adventure-story format of the first novel a good deal further, with bracing results. Every few pages, one of our two heroes mounts a daring rescue, escapes from certain death, sneaks into or out of occupied territory, or outsmarts the Germans. It's sort of like a comic book, or an old-school adventure serial — but what saves it from feeling too repetitive or episodic is the fact that Westerfeld keeps the plot moving steadily forward, and the characters develop a lot (in sometimes quite surprising ways) as the story progresses.
I guess I was expecting the second book in the series to be the "dark" one, Empire Strikes Back-style. But Westerfeld, if anything, goes the other way. The characters become even more enviable their exploits become way more impressive — with Deryn even getting a bit of a promotion. There's a large dose of wish-fulfillment, but when it's married to story-telling this clever, you won't mind a bit.
So this time around, we visit Istanbul (or "Constantinople," as various characters insist on calling it, putting the reader inevitably in mind of the They Might Be Giants song) and the neutral Sultan is in danger of joining the Clanker side of the Great War, which would spell disaster for the Darwinists. Our heroes get involved in local politics and there's a fair amount of scheming and intrigue. More importantly, we get to see a wider array of weird mecha and unusual fabricated creatures — including what was inside those mysterious eggs in the first book. There's also a development in the alternate-history world-building that will immensely please fans of Nikola Tesla.