My Sister My Beloved by Edwina Mark

Through the perfumed Isle of Lesbos...the violent fevered world of twenty-two-year old Eve and her beautiful sixteen year old half sister Sheila...
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“Through the perfumed isles of Lesbos. With unerring sensitivity and tact, the author takes the reader into the violent, fevered world of twenty-two year old Eve, who didn’t know where she belonged, and of her beautiful sixteen year old half-sister, Sheila, who did. The tragic relationship between the two girls and their sadistic, alcoholic mother builds up to a heart-gripping climax that will leave you breathless”
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22-year old woman and her beautiful 16-year-old sister are driven together by a bad home life and find solace in each other. Edwina Mark is supposedly the pseudonym of a young American woman (jacket flap includes a photo of the fetching and come-hither authoress), and a member of a famous literary family. The first was untrue, the second true. Mark was really Edwin Fadiman, Jr. His first novel, but Fadiman wasn't done: he wrote two more lesbian-themed novels under this pseudonym.