The Dom, the Switch, and the Sub (Club Libertine #5)
Diane Leyne

But Zack has misread Luke's intentions. Luke isn't looking to steal Serena away. He wants both of them and will mount whatever type of campaign it takes to win them over. And Zack is shocked to realize that Luke doesn't just want to share Serena. He also expects Zack to submit to him as well.
Zack has always thought of himself as a Dom. But is he really a Switch? Can he share the woman he loves with another man? Can he be with another man?