Ursula's Revenge Book 1 (The Allan Aldiss Library)

When Ursula learns that Emma has been deceiving her behind her back with another of her girls and with a secret male lover, she plans a particularly cruel revenge - and one that is the very extreme of exerting power over a beautiful young woman.
This story was the first of the Ursula series that continued the Emma books published by Nexus and written by Allan Aldiss under the name of Hilary James. It, too, was written in conjunction with the real life Emma, a young married woman. It is based on her own true adventures whilst in the power of Ursula, a strict and terrifyingly ruthless woman, whose blandishments she can never quite shake off.
Ursula operates in a secret world in which, beautiful and outwardly independent young women are secretly the submissive and willing playthings a coterie of rich and dominant ladies. The Mistresses, in turn, enjoy not only the intense physical pleasure they obtain from their girls, but also the feeling of power that control over their protégées gives them.