The Lost Duke of Wyndham Mr. Cavendish, I Presume The Secret Diaries of Miranda Cheever - All by Julia Quinn
Just re-reading a bit of what's on my bookshelves.
"You need me. You wouldn't be much of a hero without a villain. And you do love being the hero, don't you. The cheering children, the swooning women, you love it so much, it's made you my most reliable accomplice." -- Lex Luthor to Superman, Question Authority, Justice League Unlimited