In the 1990s, Books of Wonder supplemented their deluxe reprints of the Oz books (that's... probably the best term for them) with a host of brand new Oz stories, basically in an attempt to re-launch the Oz series.
One of the big contributors to this new line of Oz books was Donald Abbott, who preferred to illustrate his stories in a manner copying W.W. Denslow. (Books of Wonder had Abbott illustrate their new edition of Dot and Tot of Merryland, which led to some fans incorrectly thinking that they'd used the original Denslow illustrations.)
It tells how Oscar was blown to Oz in his balloon and how he faced off against the Wicked Witches despite having no power, how he built the Emerald City and how Glinda helped him without letting him know who she was. It also tells how the Wicked Witch of the West got the Golden Cap and gives a peek at the origins of the Scarecrow, Tin Woodman and Cowardly Lion (even though I think all of them appear way too early in the Oz timeline to really work with the Baum stories).
I suppose it's a fine enough story, but so little happens (the book is less than 100 pages) that it's rather cut and dry. And a more satisfying account of the Wizard's dealing with Mombi was already told in Hugh Pendexter III's "Oz and the Three Witches." Joe doesn't list this Abbott story on his timeline at all.
Blinkie the Witch of the South awakens the Sand Serpent: a beast that was created to protect the Land of Oz by patrolling the Deadly Desert, but had its mind poisoned over time and then turned to attack Oz. It was put to sleep with the legendary Amber Flute, but only one person knows where that is: the villainous wizard Ozwaldo. Can the Scarecrow, Tin Woodman and Cowardly Lion trust a villain as they fight another villain?
While rather simple (Abbott cannot write a great plot twist), it was an enjoyable adventure story for our friends.