Tough choice, but I love Good Masters! Sweet Ladies!: Voices from a Medieval Village (2008) by Laura Amy Schlitz. It reflects my own fascination with the thirteenth century; you should see the row of books I’ve collected on that topic. She did such a great job that I can probably forget my own plans for a medieval-village book.
winner of the Newbery Medal in 1990 for Number the Stars
and in 1994 for The Giver