Leviathan by Scott Westerfeld

I confess that I had a lot of trouble getting into this story. I listened to the audiobook and at first it was hard to follow some of the language about Clankers and Darwinists and boffins. But it did turn out to be a really good book with some extremely cool technological ideas. It is the dawn of World War I and, as in real life, the Archduke Ferdinand is murdered, which sets all of Europe on the course toward war. In this fantasy world the Archduke has a son named Alek, whose advisors try to whisk him off to safety in nearby Switzerland. They travel in a Stormwalker—a huge walking armored vehicle created by the Clankers (the German-Austrian-Hungarian faction of the war). Meanwhile, in England a young girl named Daryn is disguising herself as a boy in order to enlist in the British air force. She gets a position on the Leviathan—a huge airship made of genetically modified creatures. (The British are Darwinists and they can manipulate DNA in amazing ways.) The crews of the Leviathan and the Stormwalker meet in the mountains of Switzerland and the lines between enemies and allies blur as Alek and Daryn form a tentative friendship. The story was good and the world of Clankers and Darwinists was also pretty fascinating. If you like this kind of story (often called steampunk) you should also try Airborn by Kenneth Oppel and Mortal Engines by Philip Reeve.