The Third Sex by Artemis Smith

One of the most famous of the Lesbian erotic novels, set on Gay Street where women came to find new thrills or special kinds of partners.

'A penetrating study of homosexuality'--Spine

To fool the world, they married. For Joan loved women and Marc preferred men!

From the back:

Joan tried to be like other girls... and she could not understand why ecstasy remained unattainable. Desperately she sought surcease in the arms of David, of Paul,of a succession of other men. But the statisfactions of love were gained only when at last she found herself passionately involved with another girl - with the blond, enchanting Ruth!

To disguise her aberration, Joan had married Ruth's brother, Marc. This made things convenient for Marc, too, since behind the curtain of propriety he could indulge his own twisted needs...

It was one of the strangest arrangements in all the strange annals of love. Could happiness possibly bless this entangled union? Or would the base instincts which fostere such unconventionality in the end not ruin only Joan, but the others?