Mr. Sallis’s work relied on the genre conventions of potboilers, yet the old-fashioned term “man of letters” was often used to capture his eclecticism and sophistication. In addition to his 18 novels, he also translated a novel from the French; wrote a biography; helped run a British sci-fi magazine; edited an anthology on jazz guitar; churned out criticism, poetry and short stories; and played banjo in a three-piece band.