The failure of the marriage between Sylvia Plath and Ted Hughes has always been considered from one of two conflicting viewpoints: hers or his. Missing for more than four decades has been a third perspective on the events that brought their marriage to its ill-fated end, the story of another -- the other -- woman: Hughes' mistress Assia Wevill. Like Plath before her, Assia shared her life with Hughes for seven years, until she took her own life and...