Paul Sloane 's first book, Lateral Thinking Puzzlers , was published by Union Square & Co. (then Sterling) in 1991, and has gone on to sell more than 400,000 copies. Des MacHale has written more than 40 books, including one on John Ford's classic film The Quiet Man and another on George Boole of Boolean algebra fame. Following a chance meeting between Paul Sloane and Des MacHale in 1991, the two have written many popular books of lateral thinking puzzles, all published by Puzzlewright.