More Than a Mistress - Mary Balogh I read this as an unabridged audio so I'll more than likely spell some things incorrectly and may be fuzzy on some of the details.

The hero, a fancy-pants duke, is injured during a duel when a young lady gives a shout out. She's held up because of the ridiculous duel and ends up getting fired from her job and can't buy groceries. She blames Jocelyn Dudley, Duke of Tresham, for her predicament and tracks him down to holler at him (a little fuzzy on the details here ~ this is why I need to take notes). Jocelyn ends up hiring her as his nurse-maid because he's unable to get around due to the injury he believes she's caused. He's all snarly and haughty and is amused by the fact that she dares to speak her mind.

As the story progresses, we learn that she's the daughter of an Earl but is on the run due to an incident where she may or may not have killed a man. She is hiding from society and fears for her future. When Jocelyn (what kind of name is that for a hunky Duke, anyway?) heals he finds he just can't let her go and proposes she become his mistress. Lots of banter and tension of the romantic type ensues. This is good stuff but then again Balogh is usually always good.