Goliath (Leviathan #3) by Scott Westerfeld (2011)

YA Fiction | Historical Fantasy | Steampunk
Blurb:

“Alek and Deryn are abroad the Leviathan when the ship is ordered to pick up an unusual passenger. This brilliant/maniacal inventor claims to have a weapon called Goliath that can end the war. But whose side is he really on?  Continue reading →