Oz Before the Rainbow: L. Frank Baum's The Wonderful Wizard of Oz on Stage and Screen to 1939, by Mark Evan Swartz - This is in overview of the earlier and lesser known stage and screen adaptations of Baum's book, from the 1902 stage play up through the 1925 silent film with Larry Semon. I find this topic rather fascinating, particularly in regards to the original play, a musical extravaganza of the sort that was popular at the time. What's odd is that it seems every secondhand source of information I read says something different about the creation of the show, mostly in terms of how much input Baum actually had. While his original script was pretty close to the book, some credit him with many of the changes that took place before the show hit the stage, while others claim Julian Mitchell was responsible. Also, I've seen it proposed that some of the songs written by Paul Tietjens with lyrics by Baum ended up being credited to other writers. Certainly, most of the hits from the play ended up being totally unrelated songs, sometimes from other musicals. It appears that many, but by no means all, of the original Baum/Tietjens songs were actually plot-related in some way. Also, neither Baum's original script nor any known version of the show included the Wicked Witch of the West. She was also absent from the Semon film, but she DID make a significant appearance in the 1910 movie produced by the Selig Polyscope Company. Considering how significant the Witch was in the MGM movie, it's weird how she'd been omitted entirely from so many earlier versions.
One bit of trivia I found interesting was the fact that some people complained that the MGM film would not include any of the songs from the stage play. The play had been a hit for years, frequently being revived by new companies, but most of the songs had nothing at all to do with Oz. Although not mentioned in the book, I also remember hearing that Ruth Plumly Thompson tried to sell MGM the songs from her play A Day in Oz. All in all, I think MGM was right to go with Harold Arlen and Yip Harburg instead. Oh, and in light of my speculation on the idea of characters from Dorothy's Kansas life being represented in Oz, Noel Langley cited his most direct influence for this to be a Mary Pickford film called The Poor Little Rich Girl. Apparently Langley and others felt that audiences wouldn't connect with the fanciful denizens of Oz unless they were first introduced to them as mundane humans. And maybe they were right, but I still see it as unnecessary. It was basically a way to make the movie both a fantasy and a non-fantasy at a same time.