Improper relations - Janet Mullany

After losing best friend and cousin Ann Weller in marriage to the Earl of Beresford, sharp-witted Charlotte Hayden is even ruder than usual to potential suitors. Introduced to Beresford's wayward cousin, Shad, Charlotte may have met her match in witty repartee - but he's hardly husband material. Caught in a compromising situation, Charlotte and Shad are forced to wed, resigning themselves to a marriage of convenience. And they aren't the only ones with marital problems...Have both Ann and Charlotte married in haste to repent at leisure? And where do their loyalties really lie? With their husbands, with each other, or somewhere else entirely?