An Heiress for August by Kathleen Ayers

London’s most notorious rake needs to wed.
August Wade was never meant to be the Duke of Courtland. Now he’s inherited the title from his uncle along with the poorly managed ducal estates. After months of attempting to remedy the situation, August concludes that he must wed an heiress. Specifically, Miss Hazel Dartmont, only child of an obnoxiously wealthy textile merchant. Not only is Miss Dartmont wealthy, but she is several years on the shelf and far beneath him socially. She will be thrilled to draw the attention of a duke. Desperate, even.

Miss Hazel Dartmont is an expert at avoiding marriage.
Hazel only accepted the invitation to Lady Talbot’s house party to escape London and the attentions of an overly amorous gentleman. As a wealthy heiress, albeit one with a pedigree most of society turns their noses up at, Hazel is accustomed to being targeted by every desperate dandy in London. Now well past marriageable age, Hazel delights in her independence and has no intention of ever taking a husband.
Not even the rakish Duke of Courtland can change her mind.