Hard As You Can by Laura Kaye

Five dishonored soldiers.
Former Special Forces.
One last mission.
These are the men of Hard Ink.

Ever since hard-bodied, drop-dead-charming Shane McCallan strolled into the dance club where Crystal Dean works, he's shown a knack for getting beneath her defenses. For her little sister's sake, Crystal can't get too close. Until her job and Shane's mission intersect, and he reveals talents that go deeper than she could have guessed.

Shane would never turn his back on a friend in need, especially a former Special Forces teammate running a dangerous, off-the-books operation. Nor can he walk away from Crystal. The gorgeous waitress is hiding secrets she doesn't want him to uncover. Too bad. He's exactly the man she needs to protect her sister, her life, and her heart. All he has to do is convince her that when something feels this good, you hold on as hard as you can—and never let go.