Forever and a Duke by Christy Carlyle

A roguish duke seeks to escape the demons of his past via a marriage of convenience with his friend’s bluestocking sister and gets far more than he bargained for.

Miss Lily Bridewell—stubborn, intelligent, and fiercely protective of those she loves—is determined to keep the misfortunes that have befallen her family from affecting her sisters’ futures. When the heir to their father’s title and estate ousts them from their family home, Lily’s desperation drives her into the arms of the one man she fears she cannot trust—especially with her heart.
Griffin Knightley, Duke of Edgerton, vowed to mend his rakehell ways when he inherited a dukedom. But he falls back into old habits one fateful night that leads to tragedy—the death of his best friend. Guilt haunts him even as he tries to become a respectable nobleman, and when his late friend’s sisters lose their home, he sees it as his duty to assist them. A marriage of convenience with the eldest would solve two dilemmas—his need for a duchess and the Bridewell sisters’ need for a home.

A simple agreement. A practical transaction. But attraction to his strong-willed bluestocking bride makes it impossible for Griffin to be the cool, levelheaded duke he’s determined to be, and Lily won’t settle for anything less than his heart.