Copyright status of The Wizard of Oz and related works in the United States
"The Wonderful Wizard of Oz" was published in 1900, and was the first to enter the public domain in "1956". This allowed Reilly & Lee, the publisher of all the other Oz books (as well as Baum's other books) to issue their own edition of "The Wizard of Oz", which had previously been published by George M. Hill Company and later by the Bobbs Merill Company after Hill went bankrupt..
Ozoplaning with the Wizard of Oz
The phrase "The Wizard of Oz" was included in the title to coincide with the MGM film "The Wizard of Oz", which was released the same year the book was published. As such, the focus of the story is on characters who appeared in the first book. Thompson focuses the book most strongly on Jellia Jamb, though that character was unnamed in the first book and was absent from the film.