Sidney’s Wife by Sheldon Lord aka Milo Perichitich (Beacon, 1964)
Boy had I hoped this would be a keen Lawrence Block Sheldon Lord in the vein of The Sex Shuffle or April North…but no, this one is not Block, it is Milo Perichitich, the lesser of the Sheldon Lords. Possible, as was the case with Nighttstand, Block stopped being Lord and Andrew Shaw after 1963 as he persued his crime fiction career and was being Jill Emerson. (Being Jill Emerson would be a great title for something.)
This one is your typical corporate suit types who lust after each other’s wives and use one another’s wife to advance or get revenge. Been there done that in pulp sleazeland. Sidney’s Wife is almost unreadable.