Leviathan, by Scott Westerfeld

Leviathan

Westerfeld, the man behind the Uglies series, turns his attention to alternate history and steampunk fiction with a flair. Set just before and at the beginning of World War I, Leviathan presents three major changes to history as we know it: Archduke Ferdinand of Austria has a son, Darwin discovered how to manipulate DNA and create extraordinary, fantastical creatures, and there are giant machines of war known as walkers (warships on land) that changed the face of war. The two main characters, Deryn (a girl disguised at a boy who serves in the Royal Navy) and Aleksandar (the Archduke’s son) provide contrasting viewpoints against an exciting backdrop of war, science, and survival.