Goliath by Scott Westerfeld (Grades 7 and up). Sequel to Leviathan and Behemoth. Alek and Deryn encounter obstacles on the last leg of their round-the-world quest to end World War I, reclaim Alek's throne as prince of Austria, and finally fall in love.
The Son of Neptune (The Heroes of Olympus Series by Rick Riordan. While lost and disoriented by amnesia, Percy Jackson discovers the other half of the demigod world, previously unknown to those at Camp Half-Blood.