The Thief by Megan Whalen Turner
Newbery Medal winning fantasy, set in a world not unlike Ancient Greece, complete with interfering Gods and Goddesses.
The King's magus believes he knows the site of an ancient treasure - Hamiathe's Gift. To attain it, he needs a skillful thief and he selects Gen from the King's prison. The magus is only interested in the thief's abilities; what Gen is interested in is anyone's guess.
A likeable rogue, Gen endures the difficult trek with much complaining and little grace, but shows his mettle when he steals the Gift twice and risks his life for his companions.
The Thief is an exciting and compelling 'road-movie' story, with a cracking twist at the end which surprises both the magus and Gen's travelling companions - not to mention the reader!!