Jade City (The Green Bone Saga: Bk. 1)

Jade is the lifeblood of the city of Janloon--a stone that enhances a warrior's natural strength and speed. It is mined, traded, stolen and killed for, all controlled by two families equal in their power and ruthlessness. When a modern drug emerges that allows anyone--even foreigners--to wield jade, simmering tension between the two clans erupts into open war.