The Libertine's Wife — Karolyn Cairns

Lady Arianne Dunne went along with her brother's rash scheme to ensnare a rich husband. In love with another man, she helps deceive the wealthy marquis who becomes a convenient means to an end.
Garret Spencer is an unrepentant libertine. He swore off marriage, living his sordid life as he saw fit. After one night of passion, he leaves Arianne in a fit of anger.
He comes back years later, unable to forget her. The past now threatens the unexpected happiness they find together. Desperate to hold onto the man who suddenly means everything to her, she gets trapped into a web of deceit once more.
Arianne soon finds herself falling in love with her unsuitable husband, finding him perfect for her before long. Garret soon immerses her in his secret world of erotic passion, daring to trust the wife he once thought was a deceiving fortune hunter.
When their love is tested in a cruel twist of fate, they face the greatest challenge of all, forgiving one another.