List of Oz books. The Oz books form a book series that begins with The Wonderful Wizard of Oz (1900) and relate the fictional history of the Land of Oz. Oz was created by author L. Frank Baum, who went on to write fourteen full-length Oz books. All of Baum written books are in the public domain in the United States. Even while he was alive, Baum was styled as the Royal Historian of Oz to emphasize the concept that Oz is an actual place.