The Grace of Kings by Ken Liu

Wily, charming Kuni Garu, a bandit, and stern, fearless Mata Zyndu, the son of a deposed duke, seem like polar opposites. Yet, in the uprising against the emperor, the two quickly become the best of friends after a series of adventures fighting against vast conscripted armies, silk-draped airships, and shapeshifting gods. Once the emperor has been overthrown, however, they each find themselves the leader of separate factions—two sides with very different ideas about how the world should be run and the meaning of justice.