Showboat World, written in 1975, is the second, stand-alone novel in a pair of science fiction novels by Jack Vance, was an American mystery, fantasy, and science fiction writer, he also wrote how many mystery novels, under the pseudonym Ellery Queen?
Jack Vance:  Though most of his work has been published under the name Jack Vance, he also wrote 9 mystery novels using his full name John Holbrook Vance, three under the pseudonym Ellery Queen, and one each using the pseudonyms Alan Wade, Peter Held, John van See, and Jay Kavanse.
i don't know