His Mischievous Minx (Marsden Descendants, #6)

Lady Emilia St. John has loved Alexander Marsden, the Earl of Devon, for as long as she can remember. Unfortunately, he also doesn't seem to notice her. She's more than aware of his roguish behavior, and hopes to use that to her advantage. It's time for him to realize they are meant to be together, and she's willing to seduce him to achieve her goal.

Alex does notice Emilia, and he wishes he didn't. She grows lovelier each day and his desire for her grows, but he doesn't believe he's worthy...