Brain of the Galaxy — Jack Vance

Arthur Caversham of 22nd-century Boston finds himself naked at a dinner party. Bearwald the Halforn battles the Brands from Mount Medallion. Ceistan seeks a parchment in the dead city of Therlatch filled with treasure that is now worthless. Dobnor Daksat is competing with artists of the top order to create worlds with the imagicon, a device unknown to him. What is the connection of these disparate tales? Not even the Brain of the Galaxy understands their full ramifications. First published in 1951, later reprinted as the The New Prime.