Wicked question

Don't worry. I didn't read any other book before this one and I didn't have any problem with the story. As long as the basic points are in the 1939 movie, you don't need anything else to get the gist. It's true that I looked for a couple of things in Wikipedia, but it was just curiosity and because I watched the movie long ago.

I think it's a good book by itself, although there are two more books related to the Wicked West Witch. I read like ten years ago and I never feel the necessity of finishing the whole trilogy.

It is a 4 book series, but it stands alone just fine. I actually didn't finish the series because the book was just okay to me. I wasn't interested in the continuation of the story. The book is very different then Frank L. Baum's books and relates more to the movie.