Leviathan series #1 Leviathan 
By Scott Westerfield  

In this book it is the beginning of World War I. The Austrians and Germans are Clankers they use steam powered machines to fight. The British are Darwinists they use fabricated animals to fight in the war. Alek, an Austrian and Deryn a Darwinist meet on the deck of the Leviathan, the best airship in the British navy and become allies even with their countries on the brink of war.

I highly recommend this book for older readers. (probably not younger than 11) it was a really great book.       
                                                                       review by Bookworm age 11