The Middle Kingdom: Book 3: Chung Kuo by David Wingrove
The great Empire of Ice - Chung Kuo - has finally been shaken after more than two centuries of peace enforced by brutal tyranny. The Minister of the Edict has been assassinated and the seven ruling T'ang struggle to maintain Stasis, even as their mile-high, continent-spanning cities descend into chaos. But the assassination was orchestrated by men close to the ruling powers; powerful merchants - Dispersionists - intent on Change, whose betrayal will lead them into the world-shattering War of the Two Directions.