The Lost Princess of Oz is the eleventh canonical Oz book written by L. Frank Baum. Published on June 5, 1917, it begins with the disappearance of Princess Ozma, the ruler of Oz and covers Dorothy and the Wizard's efforts to find her. The introduction to the book states that it's inspiration was a letter a little girl had written to Baum: "I suppose if Ozma ever got hurt or losted, everybody would be sorry."

The Wonderful Wizard of Oz, is an American children's novel written by author L. Frank Baum and illustrated by W. W. Denslow, originally published by the George M. Hill Company in Chicago on May 17, 1900. It has since been reprinted on numerous occasions, most often under the title The Wizard of Oz, which is the title of the popular 1902 Broadway musical as well as the iconic 1939 musical film adaptation. The story chronicles the adventures of a young farm girl named Dorothy in the magical Land of Oz, after she and her pet dog Toto are swept away from their Kansas home by a cyclone. The novel is one of the best-known stories in American literature and has been widely translated. Its groundbreaking success and the success of the Broadway musical adapted from the novel led Baum to write thirteen additional Oz books that serve as official sequels to the first story.