Shea was born to Irish parents in Los Angeles in 1946. There he frequented Venice Beach and the Baldwin Hills for their wildlife. He attended UCLA and Berkeley and hitch-hiked twice across the US and Canada. At a hotel in Juneau, Alaska, Shea chanced on a battered book from the lobby shelves, "The Eyes of the Overworld" by Jack Vance (1966). Four years later, after a brief first marriage and one year hitch-hiking through France and Spain, he wrote a novel in homage to Vance, who graciously declined to share the advance offered by DAW Books. It was Shea's first publication, "A Quest for Simbilis" (1974), and an authorized sequel to Vance's two Dying Earth books then extant. ISFDB notes that it "became non-canonic" in 1983 when Vance "continued ... "The Eyes" ... in a different direction."