An American novelist and journalist, he co-authored the Illuminatus! fantasy trilogy with Robert Anton Wilson. Shea's other works include Shike; All Things are Lights; The Saracen; and From No Man's Land to Plaza del Lago.
Before beginning his fiction writing career, he wrote for Playboy magazine.
His final novel, Children of Earthmaker, remained unfinished at the time of his death.
He was married twice: first, to Yvonne Bremseth Shea, and later to writer Patricia Monaghan.
He and Cherith Baldry both wrote fantasy novels.