This is the most powerful novel you will ever read on the subject, written by a woman who is, hersefl, A TORMENTED LESBIAN!
Harlan Ellison wrote the purple prose cover copy, and I am sure he had a laugh when composing this: The second Marlene Longman, however, Lesbian Love, was penned by Marion Zimmer Bradley, and tends to be pricey among colletors, up to $200 as seen here. Sin Girls is Nightstand #1514, the 13th book William Hamling published in early 1960, written by Robert Silbverberg.
