In His View by SE Honeycutt

Izzy Chandler’s life is going perfectly to plan. She has a window office in her design firm, a soon-to-be fiancée, and a swank condo in a downtown highrise. But the perfect life she thought she had begins to crumble after she meets the handsome and mysterious new penthouse owner, Michael Dufrey.
Soon after, Izzy finds herself caught in the sights of the man in black, a notorious contract killer, who sees nothing but vengeance. She finds an unlikely ally in Michael, who seems to have a lethal and tactical background and an equal thirst for revenge.
Caught in the middle of this cat-and-mouse game, Izzy finds herself in a web full of deceit and learns the man she was supposed to spend the rest of her life with is not the man she thought he was. Fighting her growing attraction to Michael is the least of her worries as she must find a way to save her life and those she holds most dear.