The Courtship Calculation by Laura Trentham

Damien Northcutt is a gambler, a rake, a bastard, and… bored. Madeline Barnes is a botanist, a lady, an innocent, and… curious.

When Damien accidentally plays knight-errant and rescues Madeline from the clutches of her scheming relatives, he discovers she might be the key to getting what he’s always wanted—revenge.
Even though Damien has warned her repeatedly he is no gentleman, Madeline is sure deep down underneath his rakish demeanor he is a hero. Why else would he secret her out of a ball to safety?
Damien’s plan includes seduction but not marriage. What he doesn’t expect is being seduced himself by Madeline’s smiles and laughter and passion. But she is meant for Damien’s half brother, and enacting his revenge means ruining the match… and breaking her heart.