I have just bought one of Elizabeth’s St John’s books (although not a medieval one) - I need to go back through this thread & add more of the recommendations to the wish list.
If anyone likes the Decameron, then there is also the Heptameron of Marguerite de Navarre (it’s early French Renaissance rather than medieval but it uses the same format of people brought together by an event telling each other stories). It’s another text that I thought about when reading Kristin Lavransdatter as it gives a woman’s perspective. One of the stories is about an attempted assault by a man hiding in a woman’s bedchamber & I have read that this might have been inspired by Marguerite’s own experience - it is chilling to think that even a King’s sister was not protected from this (as if she wasn’t then then nobody else would have been protected either).
Also very late medieval / early Renaissance is Fortune, Misfortune, Fortifies One by Shirley Bonner about Margaret of Austria.
House of Lilies by Justine Firnhaber-Baker is a very readable account of the Capet dynasty in France (it tells the other side of the story to our Plantagenet history).
Nancy Goldstone has written about Eleanor of Provence and her sisters and also about Joanna of Naples, which are very readable (although I preferred her books about the Winter Queen (Elizabeth Stuart) and Catherine de Medicis and her daughter Margot de Valois).
Marc Morris has written about the Anglo-Saxons and about later medieval kings including King John
and Edward I.
Not a book, but on the Gone Medieval podcast there should be some episodes where Matthew Lewis debates with Nathan Amin about the Princes in the Tower (they have opposing views about this issue so you get both sides of the debate).
Juliet Barker has also written about Agincourt (I found her book as Bernard Cornwall recommends it in his novel).
I’m a bit surprised by how many books I have about the Middle Ages, but these are the ones I remember enjoying. Some I haven’t read, so I probably could do with having a medieval focus to my Read What You Own next year!