A writer and former magazine editor, Og Mandino published The Greatest Salesman in the World in 1968, a parable with common sense advice on how to succeed in life. The book was a success and Mandino became one of the most popular motivational speakers in the U.S. He went on to write other self-help books, including The Greatest Secret in the World and A Better Way to Live. All told, Mandino has sold more than 30 million books.