Roger Zelazny's To Rule in Amber (Dawn of Amber Trilogy Book 3)

Oberon takes on the reins of leadership, and he carves an empire from the new universe created by his father. Enemies new and old lie in wait, and creating a kingdom for himself and his heirs requires delicate political maneuvering, a will of iron, and the might of a born warrior. Power-mad siblings, a madman for a father, assassins, and the King of Chaos are just the beginning of his troubles. Oberon must learn to master them all, if he is To Rule in Amber.