Not that Kind of Girl by Catherine Alliott

A girl can get into all kinds of trouble just by going back to work ...Henrietta Tate gave up everything for her husband Marcus and their kids. But now that the children are away at school and she's rattling round their large country house all day she's feeling more than a little lost. So when a friend puts her in touch with Laurie, a historian in need of a PA, Henrietta heads for London. Quickly, she throws herself into the job. Marcus is - of course - jealous of her spending so much time with her charming new boss. And soon enough her absence causes cracks to form in their marriage that just can't be papered over. Then Rupert, a very old flame, reappears, and Henrietta suddenly finds herself torn between three men. How did this happen? She's not that kind of girl ...is she?