Heraldry, Pageantry and Social Display in Medieval England, edited by Peter Coss and Maurice Keen. This is an academic collection of articles on the topic. I've actually read it before, or most of it, but I'm particularly enjoying "Knighthood, Heraldry and Social Exclusion in Edwardian England" by Peter Coss (that's the first three Edwards, not Edward VI, by the way) and "Heraldry in Medieval England: Symbols of Politics and Progaganda" by Adrian Ailes.
I just finished re-reading Living and Dining in Medieval Paris: The Household of a Fourteenth Century Knight by Nicole Crossley-Holland. So useful and entertaining I decided at last to order my own copy and to stop monopolizing the MSU library copy.