Being the earliest chronological entry in the series, the Scarecrow’s reunion with the Tin Man and Lion as a means to celebrate the second anniversary of his coronation is interrupted by Jinjur’s invasion.
Also, the Tin Man and Scarecrow escape on Lion which is different than them along with Tip and Jack Pumpkinhead escaping the invasion by use of the flying Gump.
Jinur kills the "Army of Oz" as the invasion included gunfire, but in canon, her Army of Revolt was rather peaceful and only threatened to poke people with sewing needles until they complied.
It is presumed that Glinda took Ozma out of Gillikin Country out of the custody of Mombi but this has yet to be mentioned in detail.
Before her death, Hibiscus Lemon mentions Ozma, but she could have been referring to a previous Ozma in a concept similar to that which is mentioned in the Oz books and the Wicked series.
The titles and descriptions of in-universe books are mentioned as:
53 volumes of The Collected History of Oz: Its Landscapes, Customs, and Peoples (Scarecrow was only on Volume 23)
Anthropmorphicum Catalogarium: A Bestiary of Magical Creatures, Their Diets & Their Habitats
Tax Codes of the Quadlings
How to Cook for a Rigmarole
Despots of Oz: Their Way, or the Highway! which he uses to look up General Jinjur who had been planning her invasion for a long time but paused after hearing Dorothy companions had been given "mighty gifts of magic". Interestingly enough, other entries include articles about: Chiss, Dr. Pipt, Eureka (she had orginally came to Oz in Dorothy and the Wizard in Oz), Evoldo (he had been dead before the events of Ozma of Oz), Gayelette, and the Hungry Tiger.