Big Gun

Gunner. He's hot, he's young, and he has so much to offer but his forty-year-old cougar can't commit. 

Why? Because she's his Battalion Commander and she's more than just afraid of getting caught with her subordinate. She's afraid of robbing Gunner of a future she thinks he deserves. But none of that matters to a man who wants what he's done his duty to protect. So, no matter how hard things will get between him and the woman he loves, Gunner is not going to go down without a fight.

This is book one in the American Badass series by Dani Stowe.