Oak: The Frame of Civilization by William Bryant Logan. Relationship between humans and oak trees since time immemorial. From boats to wagons to barrels to tables to swords. Multidisciplinary study of the oak tree from all angles.
France in the Middle Ages 987-1460, by Georges Duby. A resource for the novel A SONG FOR ARBONNE. GGK writes, "There isn't a single work of his that I don't recommend for those seriously interested in the medieval period, especially in France (though he is NOT light reading). Duby lived down the road from us on one of our stays in Provence. I still regret never meeting him to say how much I respected his work."