This erudite critical study, together with the Unabridged Diaries of Sylvia Plath released last year, breathes new life into Plath scholarship, ironically in this case through the study of her husband's poetry, particularly Birthday Letters (published in 1998 shortly before his death), which, Wagner, literary editor of the London Times, asserts, ""demonstrates the extent to which the poets influenced each other,"" and then goes on to offer ample evidence, grounding particular poetic images and phrases in specific events of Plath's and Hughes's lives. Hughes's love poetry in Birthday Letters overtly refers to his first meeting of Sylvia at Oxford: ""Maybe I noticed you./ .../ Your exaggerated American/ Grin for the cameras, the judges, the strangers, the frighteners."" Another poem, about their honeymoon to Spain, notes that ""Spain/ was the land of your dreams: the dust-red cadaver/ You dared not wake with...."" To understand the complexities of Hughes and Plath's relationship, however, Wagner has had to touch upon one of the literary world's most controversial, and often ugly, disputes: to what degree if any did Hughes contribute to his wife's depression and subsequent suicide at age 30? Fortunately, Wagner is not interested in either launching crude attacks on or apologizing for Hughes. Her clear and careful scholarship allows readers to come to their own conclusions. She encourages readers to stop playing the blame game with these two gifted poets, whose work and lives were undoubtedly influenced by their marriage to each other. In Wagner's own no-nonsense phrasing, her superb study ""is an attempt to open up this dialogue between two people both now dead and make [it]... more accessible to the general reader."" 8 pages of photos not seen by PW. (Apr.) Forecast: The publication of Birthday Letters created quite a stir. With the recent publication of Plath's unabridged diaries, and Wagner's moderate attitude toward the Plath/Hughes debate, which will undoubtedly be controversial, this could see lively sales.