Leviathan by Scott Westerfeld

Set at the beginning of World War I, this story follows an alternate path. The assassination of Archduke Ferdinand and his wife remain the same but their son Alek is wisked away before he too is murdered. This one act sends countries around the world into war only in this alternate universe the war is fought between the Clankers, who believe in machines, and the Darwinists, who uses technology to develop new species. Alek and his four faithful followers flee Austria in a Cyklop Stormwalker similar to a walking tank, hoping to reach Switzerland and safety. Meanwhile Deryn, a girl who wants to be an airman for the British, masks herself as Daryl, because the British Air Service only accepts boys. She is lucky enough to serve on the Leviathan, a enormous flying biological ship resembling a whale. When the Germans attack, Leviathan crash lands in Switzerland. It is here that Alek's and Deryn's lives intermingle and only by working together will both survive.

Leviathan is intriguing, creative, action-packed, and a thoroughly good read. Westerfeld mingles the two stories perfectly and the events ring true. The creativity of the Clanker machines and the Darwinist creations is amazing. This book is totally different from what is out there. The ending definitely lets the reader know there is to be a sequel.