Goliath by Scott Westerfeld

This book finds Deryn, Alek, and the Leviathan on a journey around the globe, first to rescue inventor Nikola Tesla, then to get him and his doomsday machine to New York to support the war effort. Along the way there are some highly interesting stops where Pancho Villa, William Randolph Hearst, and Sakichi Toyoda make appearances. I really like the alternative history in this book--Westerfeld has done a great and imaginative job figuring out how these technological differences (Darwinists who alter DNA to build beasties to do magnificent things, and Clankers who build machines) would play out in an historical context. The best part of the story, though, is all about how Deryn and Alek finally learn to trust each other.