THE dancing epidemic of 1518 was the last of its kind. Victims were gripped by the urge to dance almost endlessly. Some danced until their feet wore down to bone, and many died. John Waller explores the atmosphere of fear and superstition that created this mass hysteria, then tells how it retreated in the face of advancing rationality. The clumsy discussions of neuropsychiatry don't spoil the interesting descriptions of an age more subject to collective madness than our own. It's a book to make you grateful for the historical increase in human sanity.