Never Say Duke by Erica Ridley

Yes, Virginia, there is a Viscount…

Miss Virginia Underwood cannot resist rescuing a stray. Her latest find turns out to be a surly, reclusive war hero trying to recover from his wounds in peace. He doesn’t want her help—and Virginia definitely doesn’t want to fall in love. Not when a future with him would mean returning to the the same haut ton who laughed her out of Town during her very first Season.
Theodore O’Hanlon, Viscount Ormondton, sequestered himself far from London to heal in anonymity. For now, he can be himself. As soon as he returns, he’s meant to wed the woman his father selected years before. But when Miss Underwood turns his carefully mapped life upside-down, Theo must decide which battles are truly worth fighting for.