After Baum's death in 1919, publisher Reilly & Lee continued to produce annual Oz books, passing on the role of Royal Historian.
After Thompson, Reilly & Lee published seven more books in the series: three by John R. Neill, two by Jack Snow, one by Rachel R.C.
These are: Queen Zixi of Ix, The Magical Monarch of Mo, The Sea Fairies, Sky Island, The Life and Adventures of Santa Claus, and John Dough and the Cherub.
The Expeditioneers, as they call themselves, learn the meanings of these fortunes as they progress through an Art Colony, a Game Preserve, and a long and complex subterranean journey.
The social strife described in The Wicked Years indicates that the two series are set in similar and internally consistent but distinctly separate visions of Oz.
Alexander Volkov was a Russian novelist who published his own series of Oz novels called the Magic Land books, for readers in Soviet Russia, China and East Germany.