The Assassin The Grey Man And The Surgeon, by D. C. Stansfield

In this gritty novel, a retired assassin suffers a personal loss which triggers his desire for extreme retribution. He calls upon two former colleagues, the Grey Man, who is adept at surveillance, and Surge, who is violent muscle.

This isn't great literature, but for a fast action read it is absolutely worth the price.

The Assassin The Grey Man And The Surgeon