A Wizard in Absentia

From the back cover of the Ace first edition: "His father's a warlock; his mother, a witch. Or so it seems on the planet Gramarye, where modern technology is the ultimate "magic." Now Magnus Gallowglass is leaving his family and his home - in a starship driven by the brain of the robo-horse Fess. It's one small step for science... one giant leap for wizardry!"