Dungeon Master by Golden Angel

Rule Zero: The Dungeon Master Makes the Rules. Ten years after divorce, Leah is finally ready to move on. No more ex-with-benefits at the club she and her ex belong to. No more scenes together, no matter how hot they are. She's ready to find someone to spend the rest of her life with. So is her ex, but then Gavin drops the bombshell: he wants to move on by winning her back. Unfortunately, he might already be too late. When he shows up to declare his intentions, Leah's on her way out the door for a date with someone else. Gavin won her heart once and he's determined to win that battle again, no matter the odds.