William Peter Blatty:
In the early 50's he worked for the Psychological Warfare Division, USAF.
A Lebanese American, he first made a name for himself as "Prince Xeer", a fictitious blacksheep son of King Saud of Saudi Arabia. He even appeared as this character on "You Bet Your Life" reportedly conning Groucho.
In 1960 he published "Which Way to Mecca, Jack?".
Reading of the first chapter.