Surrender to Sin (Fallen, #1)

To save her, he must ruin her.

Lord Sebastian St. John, dedicated bachelor and a co-owner of Fallen, the most scandalous pleasure club in London, is known as Sin for good reason. Orphaned by a shocking accident, Sin long ago vowed a life of solitude and decadence. Yet when Lady Grace Carrington begs for his help destroying her reputation, Sin can't turn the ton's most proper lady away.

Obedient daughter, wife, and young widow, Grace has had enough of being controlled. After her father arranges a second loveless marriage to an eminently respectable ancient, Grace plans a fortnight of defiance and self-ruination to stop the wedding. But as Grace enters the heady, risky world of an affair with Sin, she finds herself inexplicably drawn to him— and she soon realizes two weeks won't be nearly enough.

Fun fact: the Fallen pleasure club is inspired by three real-life Regency-era clubs in London. The White House in Soho Square (madam Theresa Berkley specialized in flagellation, birching, caning etc); The Nunneries in King's Place (madam Catherine Windsor, very exclusive and a favorite of royals, MPs, diplomats, and peers); and Miss Fawkland's Temples in St. James's St.