Accidental Prince by Michelle Willingham

Princess Serena of Badenstein intends to flee – from her violent father and from the man to whom she's been pledged in a political marriage of convenience. Karl von Lohenberg is without a country, a title – and a bride if he lets Serena get away.

A ruthless man, he takes her to a secluded island, hell-bent on seduction. Only he discovers a broken woman behind the prim princess façade. The time they spend together mends her spirit and touches his soul, but how will she react to his deception?