There is a history book which I have read which I strongly encourage all those interested in Sagas set in either Normandy or the Provencal Tribunals to also read.
"The Discovery of France: a historical geography from the Revolution to the First World War", by Graham Robb (2007).
Despite the subtitle, the first half of the book delves back centuries earlier, exploring aspects of French geography, culture, and history which are almost wholely neglected in other works. Robb's work has more than 50 pages of endnotes and bibliographic information supporting his research, involving some of the earliest ethnographic surveys made of France.
Of particular interest to Mythic Europe were the prevalence of places in which entire communities and bandit armies (up to thousands strong) could "hide in plain sight", vanishing into the forests and among the steep hills of the supposedly completely developed and "civilised" regions of France. Many locales had extreme idiosyncracies and unique traditions going back to or before the Middle Ages, and many a parish observed practices which would be deemed heretical anywhere else. The map of regional dialectics and subdialects is extremely useful.
Once you've read the book, I don't think that most will ever be able to contemplate France the same way again.