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..
The Making of The Wizard of Oz
The Making of the Wizard Of Oz, written by film historian Aljean Harmetz, is a book about the production of the 1939 film "The Wizard of Oz". It was the second book ever published documenting the making of this film, released a year after Doug McClelland's 1976 work "Down the Yellow Brick Road".