The Wedding Gamble (Wellingfords #1)
Julia Justiss

Now ironic circumstance had wed her to the compelling Marquess of Englemere, a fabled gamester, who had awakened passions she was honor-bound not to express.
A marriage of convenience could be deucedly inconvenient -- even for a marquess -- when one was perilously close to loving his own wife! But that was impossible, Nicholas Stanhope knew, for hadn't his tragic past proven that women -- especially wives -- were not to be trusted?