Never Cheat Alone by Orrie Hitt

A novel about lonely woman on the prowl for sex - including sex with each other, Ultra - sophisticated.

From the back cover teaser:
BETH is the pretty wife of a sort of male nymphomanic. Maybe that's why she becomes sizzling diversion for any guy - or gal - who happens to be handy...

LIZ is a doll, in fact a doll and a half. Naturally she prefers Beth's oversexed man - but is perfectly willing to take love where she finds it...

DOROTHY is so young you would never suspect that she used to be a stripteaser. Or that she's full of unholy lust. Or that she makes out not only with men but with other women...

A torrid trio. In this blistering novel you observe them doing their thing, the sex thing. You watch them mix, mingle, and mate - until they become a tangle of twisted bodies and tortured souls. You see them learn what you knew all along: even for passion-hungry women, a continual diet of physical pleasure can be ultimately ruinous.