The Lost Princess of Oz is the 11th and last book in the Land of Oz series. It begins with the disappearance of Princess Ozma, the ruler of Oz and follows the efforts of Dorothy and the Wizard to find her. Lyman Frank Baum was an American author of children's books, best known for writing The Wonderful Wizard of Oz. He wrote thirteen novel sequels, nine other fantasy novels, and other works.