Book VIII of The Chronicles of Amber.  Amber – the one real world, of which all others are shadows…Merlin, son of Prince Corwin, pursues his noble destiny against a shifting panorama of shadow worlds and deadly intrigue, powerful computers and magic gone out of control. A violent vendetta, renegade sorcery and whirlwind adventure lead Merlin to a confrontation at the Keep of the Four Worlds, where astonishing secrets and mysterious identities will at last be revealed. Cover art by Tim White.