The Return of the Duke by Grace Callaway

When Fate throws tinker’s daughter Fancy Sheridan into the arms of Severin Knight, the Duke of Knighton, neither are prepared for the consequences. Fancy, who has always dreamed of a passionate fairy tale love, finds herself wed to a stoic nobleman whose heart belongs to another. Knighton, who needs a high-born lady to shepherd his illegitimate half-siblings through the ton, now has a wife who knows nothing of society and cares even less about its rules.
Fancy and Knighton’s marriage of convenience is further complicated by the desire that smolders between them. By day, Fancy works to transform herself into a proper lady, but by night her powerful duke’s caresses arouse her most wanton fantasies. Knighton, in turn, is captivated by his plucky and resourceful duchess, whose sweetness unleashes his deepest carnal desires and slowly forces him to confront the truth of his own heart.
As the slow burn of the Knightons’ marriage reaches a fever pitch, dangerous secrets rise from their pasts to threaten their happiness. To survive, Fancy and Knighton must lay bare their hearts and vanquish their darkest demons. Will they risk everything to win their happily ever after?