J.K. Rowling’s 2020 children’s novel about a cruel ruler is The Ickabog.
The Ickabog is a standalone political fairy tale set in the fictional kingdom of Cornucopia. Its plot follows the effects of fear, propaganda, corruption, and power as the kingdom’s leadership uses the legendary Ickabog to control public opinion.
Rowling originally wrote the story for her own children years earlier, then revisited it during the COVID-19 lockdowns. She released it online in installments beginning in May 2020, allowing children and families to read it while schools and normal activities were disrupted.
The printed edition was published in November 2020. The book is separate from the Harry Potter universe and is not a sequel to that series.