The Lost King of Oz, from 1924, re-introduces the wicked witch Mombi - last seen in The Marvelous Land of Oz. In this book, Ruth Plumly Thompson attempts to tie up some of the loose ends that L. Frank Baum left floating through the Oz series. I always liked Mombi, and was glad to meet up with her again. Having had her magical powers removed, the old woman became a cook, and developed some rather amazing culinary products and abilities.
I like the cover of this book - the colors are vibrant, and I think it is one of the nicer images of Ozma. She still appears to be a young girl, and has not morphed into the dragon lady that she appears to be in some of the later books!
I know of one illustration surviving from this book - the drawing for the color plate shown on the right. As was usual, the original is drawn in black and white, and the colors were added by the printers when printing the book. Since one drawing survived, perhaps a few others did as well!