Still the One by Jill Shalvis

Darcy Stone is game for anything — except sexy Navy veteran and physical therapist A.J. Colten, the guy who’d rejected her when she’d needed him most. Now the shoe is on the other foot and he needs her to play nice and help him secure grants for his patients. Unfortunately, Darcy can’t refuse. She needs the money to fund her passion project: rescuing S&R dogs and placing them with emotionally wounded soldiers.

A.J. admits it — Darcy is irresistible. But he’s already been battle-scarred by a strong-willed, vivacious, adventurous woman like Darcy, and he’s not making the same mistake twice—until he and Darcy are forced to fake a relationship. Growing closer than they’d ever imagined possible, Darcy and AJ have to ask themselves: how much between them is pretend? What’s the real thing? And where does it go from here?