This isn't the movie version from 1939, nor any of the "new Oz books" out there, but the original book Baum wrote in the beginning of the 1900's. You can see where the movie comes from, and some of the changes that were made in the screenplay - mostly to allow for the technology of film making in 1939. You can also see where modern authors have taken from the original to expand on what happened in Oz while staying largely true to Baum's original.