Looking for a Regency Romance book, HELP!

The story went like this:

Man returns to his home to claim the inheritance his mother left him of her family home, meets his father's new soon-to-be bride, is taken by her beauty, and is enchanted later that night by the vision of her in her nightgown in the library as she stands upon book steps to reach a book.

The reason she is marrying his father is so she can be reunited with her child, her son, I think, though I didn't read far enough to learn how marrying him will help her.

A son falls in love with his father's fiance, the fiance falls in love with the son kind of story.

Sound familiar to anyone?