Oh, man, that takes me back. I think I read everything by Jean Plaidy back in the day, and yes, it is a metric ton. I'm not surprised they seeped out of your head, they were fairly forgettable as literature goes, but they were super useful for me in retaining history. My MO for history in high school was nonfiction to know what to believe, and historical fiction so I had a hope of retaining it. So it's partly thanks to her that I remember any European history outside the 18th century.

Haha, I read a Stephen/Maud-shipping romance that, while it was full of inaccuracies and implausibilities, was probably responsible for more of my vague memories persisting to this day than the few actual histories I read.