Dark Horse by Gregg Hurwitz

Gregg Hurwitz's New York Times bestselling series returns when Orphan X faces his most challenging mission ever in Dark Horse. Evan Smoak is a man with many identities and a challenging past. As Orphan X, he was a government assassin for the off-the-books Orphan Program. After he broke with the Program, he adopted a new name and a new mission--The Nowhere Man, helping the most desperate in their times of trouble. Having just survived an attack on his life and the complete devastation of his base of operations, as well as his complicated (and deepening) relationship with his neighbor Mia Hall, Evan isn't interested in taking on a new mission. But one finds him anyway.