This is a happy surprise, a straightforward treatment of the Middle Ages without fear or favor. It's also the third large book -- in size and scope -- on the general subject this season. The Pageant of Medieval Art and Life (p. 700-J238) is art history within a social-political context: World Within Walls (p. 910-J300) is political history based on biographies of representative figures; this is social history with a minor in cultural affairs. In discussing the life of the people, the common overemphasis on property is corrected by focusing on the peasant who supported the whole structure. The ""darker side of chivalry"" is illumined and the author concludes that ""the spirit of the medieval age was savage and ferocious."" The church does not escape scrutiny; Mr. Williams comments, in quoting Chaucer, that ""he makes clear the contradiction between the rules and ideals of the religious orders and the ways their members actually behaved."" The contradictory spirit of the age is cited repeatedly, in science for the combination of ""magical recipes and practical methods."" Whether read straight through or consulted for particular topics, this is stimulating, lucid and exceptionally well-organized. A fine achievement, equally suitable for older readers.