Baum weaves a plot in which the villainous Nome King schemes to conquer Oz with the help of a succession of horrible, evil races of creatures - the Whimsies, Growleywogs, and Phantasms.
Meanwhile, Princess Ozma has decided that Dorothy, Aunt Em, and Uncle Henry may live happily ever after in the immortal fairyland. They begin their new life by touring the countryside, visiting strange settlements and meeting queer denizens along the way.
After the Fountain of Oblivion prevents Oz’s obliteration, Ozma decides that this was too close a call. From now on, Oz will be shut off forever from outside visitors through the protection of a Spell of Invisibility. Imagine the shock of Baum’s little readers upon learning that this would be farewell.
Of course modern readers know full well that the children demanded more of their favorite fairyland, and Baum eventually obliged by writing eight more Oz books.
Telling apart the different printings of this book is fairly easy.
Only the first printing shows the Wizard, Dorothy, Aunt Em, and Uncle Henry riding a carriage drawn by the Sawhorse through the Emerald City, with Ozma, the Scarecrow, and Tin Woodman looking on.
The second printing has a different cover showing Ozma flanked on either side by vase-like devices with the tops of the torsos and heads of the Tin Woodman and Scarecrow popping out. Several successive printings use this same cover design. These later printings can usually be distinguished by noting the list of titles on the verso of the ownership page.
Starting in 1929, the publisher - now known as Reilly & Lee - introduced a third cover depicting Ozma riding the Sawhorse. This is sometimes known as the "Sexy Ozma" cover, and it was used until shortly before the publisher issued its final "white edition" in 1964. (For a brief period between 1959 and 1963, the book was published with a blank cloth cover.)