Heart of the Devil (Forge Trilogy 3) by Meghan March

In this final volume, ruthless billionaire Jericho Forge faces his toughest challenge. To emerge victorious, he'll have to give up the one thing he's never offered a woman—his heart.

It started as a game. She was nothing but my pawn. But I was quick to see the error in my ways, and now she is everything I never knew I needed. The value of a woman like India Baptiste is beyond measure. But the problem with being a man like me? I've already screwed this up, and there's no guarantee India will take me on for one last bet. I'll do whatever I have to do. Drop to my knees and offer her the only thing I have left. The one thing that's only ever been hers—the heart of the devil.