This is a wonderful book, and exactly the sort of thing I needed to get started. Please thank your friend for suggesting it. It is informative, accessible, rigorous and entertaining. It has a solid bibliography too.
I have also found a good book on daily life in Dark Ages Scandanavia (Viking Age: Everyday Life During the Extraordinary Era of the Norsemen, by Kirsten Wolf). It is much less informative, as there is much less information (hence “dark ages”). Much as I like that context as a setting, it will probably be too much work for too little gain to build a game world on it. A shame, as it was my top choice for a while.
There is much more information available on 14th century England, which means I spend less time filling in the gaps with my own suppositions. The more unpleasant aspects (marrying the girls off when they’re 12, for instance) can be tweaked with little effort. Plus, who wants to play a medieval fantasy with no castles, knights, longbows, or chivalry? The advantage of writing a game in such a setting is its familiarity to players.
From Mortimer’s book, on the garderobes of the nobility:
Wherever you go, a neat pile of wool or linen will be provided for you to “wipe your nether end” [Furnivall, Babees Book, pp. 179-80]. Some great lords insist on cotton but it is not always available. A basin and jug of water will be ready for you to wash your hands when you have finished.