The Giant Horse of Oz

The Giant Horse of Oz was Ruth Plumly Thompson's title for 1928, and with this book Reilly & Lee changed the format of Oz dust jackets. Up to this point, the jackets on the Thompson titles consisted of white paper with front and back panels reproducing the cover plate of the book, and a spine panel printed in blue with the book title, an illustration and the publisher's name. The front flap had a blurb for the story and the rear flap had a list of titles, ending with the most recent title. The information on the jacket didn't change, but from this point on through the rest of the series the spine was printed in color, creating a more colorful and attractive wrap around jacket.

This idea had been visited by Reilly & Britton in 1913 with The Patchwork Girl of Oz, and before that with Sky Island. In both of those cases, the elaborate dust jacket image was different from the book cover.