I read it in my youth and loved some of it. I remember discussing it with Anne (maybe also with you?) and being shocked to discover it was alternate history. I mean, I recognized that parts were as over-the-top as Pippi Longstocking, but the frame story of the wicked Hanoverians trying to overthrow the king? I knew so very little about UK history that seemed perfectly reasonable.

Joan Aiken wrote lots and lots of other books in many genres. My particular favorites are the stories of Mark and Harriet Armitage. Before they were born, their mother wished on a magic ring that she would have two children with curious and energetic natures who would never be bored. After Aiken's death, those stories were collected in The Serial Garden and last year I got to introduce them to Vicki and Andy.