In the Empire of Shadow

SORCERY, SCIENCE, AND SHADOWS
Pel Brown knew nothing about parallel universes, let alone travel between them. Then he stepped through a portal that appeared in his basement--and his life turned upside down.
That first inexplicable doorway took him into a magic world called Faerie, ruled by the evil and mysterious Shadow. Another portal provided escape to a world of science and spaceships--and ruthless space pirates plundering the Galactic Empire.
Imperial forces rescued Pel. They would even send him home--but only after he returned to Faerie and destroyed Shadow. And so, with wizards, spacemen, and swordsmen as his unlikely allies, Pel set out to beard the enemy in its stronghold.
But real life is what happens while you're making other plans--as Pel learned when he uncovered his malign foe's true nature...