Recently we ran into a case ofwhat might be called literary predestination. Public demand for a book which didn't exist actually produced the book and a new author as well. It all began when disk jockey Jean Shepherd was toldby a smug book clerk that a book he wanted didn't exist. Shepherd determined to have his revenge on the entire industry. He urged his listeners to go to booksellers and ask for "I, Libertine" by Frederick R. Ewing. Of course, both the book and its author were the product of Shepherd's fertile brain. Hundreds of customers demanded the book from scores of harried salesmen. The industry panicked, Consequently, next month Ballantine Books will publish "I Libertine" by Frederick R. Ewing, hardback $2.00 and paperback 35 cents. Perhaps the public has grown tired of having producers dictate what is best for it. Could this be the opening shot of a consumer's revolution? But there is a literary question which must be answered. Who authored this book? Was it Shepherd, who conceived it; of the public which created ademand for it or the ghost writer who made words for it? In short, Frederick R. Ewing - are you for real?