I absolutely adored Eloisa James's Desperate Duchesses. In fact my rave review is quoted in James's latest book, An Affair Before Christmas.
Taking place immediately after Desperate Duchesses, An Affair Before Christmas focusses mainly on new characters, the Duke of Fletcher and his wife, Poppy.
Poppy's beyond-overbearing and opinionated mother has convinced Poppy of a wife's (particularly if that wife is a duchess) duties to her husband and of what she can expect in return. And let's just say that Poppy's mother's opinions of both men in general and her daughter in particular are far from high.
So although Poppy is in love with her husband (and he with her), she's never been able to show him in, you know, the bedroom. And, after four years of marriage, it's started (started?) to become a problem.
But, along with Poppy and Fletch, An Affair Before Christmas also features Jemma, the Duchess of Beaumont, who behaved so scandalously in the first book. The Duke of Villiers, with whom Jemma was conducting a shocking chess match (no, really) in the first book, is in bed with fever, following a duel with Jemma's brother, Damon. So their chess match is postponed, leaving Jemma at a loose end... and free to get into yet more trouble.