Red posted an interesting selection of covers of The Wonderful Wizard of OZ in this post: http://redthaws.booklikes.com/post/1198152/book-cover-love-wonderful-wizard-of-oz
I'd like to add to it, but sideways. In 1939, a Russian writer Alexander Volkov published a children's book in Russia called (in translation) The Wizard of the Emerald City. Later on, he published several other books about the heroes of this novel - the girl Elly, her dog Totoshka, and their friends: the woodcutter, the scarecrow, and the lion. No names of OZ or Baum were mentioned in these books until very recently, and they have been reissued in Russia countless of times since their first publication. They were very popular, and I loved these books as a child. Only after I immigrated to Canada, I discovered that there was really a different author of those books, and the girl's true name was Dorothy. Below are a few Russian covers. They still publish these books in Russia and still credit Volkov as the author.