1935, Thompson's fifteenth Oz novel, exactly one more than L. Frank Baum had written, not counting short stories, picture books, or anything in the expanded universe. Twenty-nine Oz books (or twenty-eight, since Reilly & Lee didn't count The Wonderful Wizard of Oz, since they didn't publish it), two authors. Thompson felt her well of ideas for Oz stories was running dry, and she felt Reilly & Lee weren't doing enough to promote the Oz series. This led her to suggest that this Oz book should be the final one.
The Wishing Horse of Oz opens in the kingdom of Skampavia, across the Deadly Desert. King Skamperoo obtains some magic emerald necklaces that grant him the wish for a horse, who happens to talk and is named Chalk. He says he's from Oz, and Skamperoo decides he'll take over Oz.
In Oz, however, a grand celebration is getting underway to celebrate Dorothy and the Wizard "discovering" Oz, with virtually every character from the previous twenty-eight Oz books attending. At the banquet, the Soldier with the Green Whiskers' beard suddenly turns red. Some fear it may be a forewarning of danger. Dorothy swallows a wishing pill (the Wizard seems to have an improved recipe) and wishes that regardless of what happens, she will be able to save Oz and Ozma.
The next morning, Dorothy is surprised to find Ozma, the Wizard, Glinda, Jinnicky the Red Jinn, and every other ruler of any part of Oz and magic worker, gone. No one else notices, and a strange king, Skamperoo, is on the throne. The only person who can help Dorothy is Pigasus. Due to his psychic power of making his rider a poet, he too can remember Ozma when Dorothy rides him. Dorothy realizes they will have to look outside of Oz for help.
They head to the Winkie County, because Dorothy thinks of asking Kaliko or the King of Ev for help. They come across the Black Forest, where everything is jet black. Even worse, Dorothy and Pigasus become black as well and are caught by the Black Watch, who work for Gloma the Witch. Gloma was a witch who retreated to these woods when Dorothy killed the Wicked Witches, so Ozma is completely unknown to Gloma. Fearing that Dorothy may be trying to do her in next, Gloma uses magic to try Dorothy and Pigasus, but they manage to survive. Seeing she is bested, Gloma surrenders to Dorothy, but Dorothy assures her she wishes her no harm. Gloma is able to send the two across the Deadly Desert, removes the blacking, and gives Dorothy a box with a magic powder to create a square mile of total blackness.
They visit Kaliko first. He's frustrated at Dorothy's visit, and would prefer that Ozma stay missing. But he offers what aid he can spare. He discovers Ozma and the missing people on the top of Thunder Mountain, a place where no one has returned safely or escaped from. He also tells Dorothy that he'll send his army if she can enlist another to help conquer Skamperoo. He also gives Dorothy a box of stumbling blocks.
So, wait, Dorothy and Pigasus are on a mighty errand, and are armed with magic weapons, and have a promise for help? This sounds like it could really be Thompson's best yet!
As Dorothy and Pigasus head to the Nonestic Ocean, they find Bitty Bit, the Seer of Some Summit, who, in his completely elastic tower, sees what happened, and takes them back to Oz, where, using the magic weapons and cleverness, they subdue Skamperoo and Chalk. They restore Ozma and Skamperoo is allowed five wishes when he returns to Skampavia. So, all is right again Oz very quickly...
Back in Skampavia, the wishes are turned over to Pinny Penny, Skamperoo's wise prime minister, who uses them for the good of Skampavia: that Skamperoo may be wise and generous, that Skampavia may become rich and prosperous, that the climate and soil would improve, and then, Chalk makes a wish that the three may never be separated, and they may live long. Chalk is added in the final wish.
To me, The Wishing Horse of Oz felt rushed at the end, forcing Thompson to bring in a deus ex machina in the form of Bitty Bit. Thompson had proved she had a great imagination, so I'm sure she would have delivered a different ending, provided the time to work it out. The original edition features numerous errors, suggesting a quick, sloppy editing job as well. It is also noteworthy that this was the last Oz book by Reilly & Lee to feature color plates.
Certainly, the book is not without redeeming qualities, such as the fascinating character of Gloma, a Good Witch of the West (Eric Shanower's The Blue Witch of Oz identifies her as such). It would be worthwhile to revisit her character. Bitty Bit, the deus ex machina that he is, also seems ripe for further expansion, but sadly, these two never re-surface in the Famous Forty.
So, while The Wishing Horse of Oz may be the most exciting build up to a deus ex machina that I've ever read, it is one of Thompson's better books. I just wish she could have fleshed out the ending.
Now, even though Thompson suggested that this should be her last book, would it be?