Scott Westerfield gives us a well-written alternate history of World War I. Some of the alterations include a totally mechanized German-Austro-Hungarian enemy (called Clankers) and an Allied force made up of Britain, France and Russia called Darwinists. Clanker machines walk on articulated legs. Darwinists have developed a science that creates animal combinations that are intelligent partners in the fight. The main characters are Alek, the son of the Austrian Grand Duke and Duchess, whose assassination not only leave in him an orphan, but also starts the war; and Deryn Sharp, who gets into the British by pretending to be a boy - Dylan. Alek must run for his life with a battle damaged Clanker Stormwalker and some loyal friends. Deryn/Dylan discovers the "being a boy is hard. How do they do it all their life?" Their life paths cross, taking them on board Leviathan, a fantastic whale airship and perhaps the greatest creation of the Darwinists. These two "enemies" are forced into situations that require compromise, courage, trust and finally friendship. Their adventures will take them into dangerous and interesting places.
Product Description from Amazon
It is the cusp of World War I, and all the European powers are arming up. The Austro-Hungarians and Germans have their Clankers, steam-driven iron machines loaded with guns and ammunition. The British Darwinists employ fabricated animals as their weaponry. Their Leviathan is a whale airship, and the most masterful beast in the British fleet.
Aleksandar Ferdinand, prince of the Austro-Hungarian Empire, is on the run. His own people have turned on him. His title is worthless. All he has is a battle-torn Stormwalker and a loyal crew of men.
Deryn Sharp is a commoner, a girl disguised as a boy in the British Air Service. She's a brilliant airman. But her secret is in constant danger of being discovered.
With the Great War brewing, Alek's and Deryn's paths cross in the most unexpected way...taking them both aboard the Leviathan on a fantastical, around-the-world adventure. One that will change both their lives forever.