Eyes of the Overworld — Jack Vance

INTO BLINDING MADNESS...OR VISIONS OF SPLENDOR!

Such was the power of the priceless, magic eyes of the overworld that it could exalt their wearer to realms of wonder or plunge him into dark terror.

Now Iucounu, the Laughing Magician, has dispatched an unwilling thief, Cugel the Clever, on a fantastic quest to capture the enchanted violet lenses.

Across forests of unending marvels he journeys to a world where sorcery and science are one.