Amazon.com (ISBN 0886777046, Paperback)

Six centuries after the alien Curosa imparted the wisdom of their dying race to Adrian Sawyer and gave him three massive city-ships, two of those ships -- City of Diamond and City of Opal -- are locked in a battle for intergalactic political dominance. Now the Protector of Diamond has chosen a protege, young Adrian Mercati, and told him the hiding place of the Sawyer Crown, an artifact that will give him and the Diamond unassailable superiority over the Opal. But spies are at work, and a desperate race to find the Crown begins. Yet what neither side can see is that finding it may prove their downfall.