Return to Oz is a melding of two of the Oz books: the Land of Oz and Ozma of Oz. Okay, it's more like, "hey, we like certain aspects of these two stories -- MAKE THEM FIT, SCREENWRITER SLAVE!"
Land of Oz was the first Oz book I actually read as a child. Transgendered studies should really take a look at this story. I had real conceptual problems coming to terms with a boy who was really a girl -- as a kid that came totally out of left field for me. Maybe as an adult I would understand it better.Lucky for us you can read all of these books online, download and print the .pdf's, etc. Go for it. I think you'll find Oz is a wee bit different, darker than you remember it:
There, now go read. If you have kids: make them read. These books scarred me for life when I was young; sure, they can be happy-sappy -- but mostly they are weird as high heck.