Disclaimer: I can't discuss this book without describing some aspects of it that could be construed as spoilers, so I'm mentioning this up front in case you'd prefer to avoid them.
I somehow made it through childhood without reading this book, although of course I have seen the movie numerous times. Strangely, I seem to remember owning copies of Ozma of Oz and Tik-Tok of Oz as a child, but for some reason I didn't read this book, or the entire series - ? What a strange child I apparently was! In any case, I have now read this book and enjoyed it considerably.
The movie adaptation mainly follows the book, with notable exceptions that I assume were made to simplify the plot and create a bit more drama. It's too bad that some parts, such as the china/porcelain town and the hammerheads, were cut, but I can see why they were. Movie making is often about condensing a story into a set timeframe, and many of these incidents didn't really do much for the overall plot and were more like creative interludes. I suppose too it would have taxed the special effects department, which did a fantastic job on the movie considering that they had none of the computer-generated tricks we rely so heavily on today for special effects.
Something I really liked about the book was that the Scarecrow, Tin Woodman, and Lion all got a cool new life to lead after Dorothy left them to go back to Kansas. This was a nice detail that added closure to the story, where the movie left them hanging - we don't know what will happen to them.
All in all, this is a sweet and imaginative book for children that can be enjoyed by people of all ages.
This book has the distinction of being the first book that I read entirely on my cell phone. As the book is out of copyright, I was able to download a copy for free; the drawback, of course, is that there are no cool illustrations (I adore the art from the beginning of the 20th century, so it's a shame I wasn't able to see any original art that may be included with other editions of this book). I don't have a Kindle, so this is a nice way to always have a book or 2 on hand, and to take advantage of those times when I have to wait for something by doing something good for my brain instead of something more mindless. I still prefer actual paper books, and I probably always will, but having options is nice too.