#1 John Leslie 1940- is the author of The End of the World: The Science and Ethics of Human Extinction.
#2 John Leslie 1944-, author of Blue Moon, is a mystery writer who lives in Key West, Florida.
The author of Harlequin romances including Night of the Nile is more correctly #3 Lynn Leslie.
#4 John Leslie (or Lesley) 1527-1596, author of De origine, moribus, et rebus gestis Scotorum libri decem, was a Scottish Roman Catholic bishop and historian.
#5 Sir John Leslie 1766-1832 was the author of Geometrical Analysis, and Geometry of Curve Lines.