Jack Pumpkinhead of Oz (the Wonderful Oz Books, #23)

This book gives a major role to Jack Pumpkinhead, a character who never really had one in the Baum books. In this story, Jack must test the capacity of his pumpkin seed brains, and he really does come up with some clever ideas. With the help of the Red Jinn (who becomes a more important character in later books), he eventually manages to save all of Oz from a restless and ambitious baron. As is usual for Oz books, this one contains a lot of clever new creations, including an Iffin, a baron with a never-ending beard, and a runaway Christmas tree intent on finding new ornaments. There are also many new magical items, and some well-written sequences, including the description of the main characters' entrance into the fortress city of Baffleburg. While not one of the best or most important Oz books, it is definitely a fun read.