Like a Hole in the Head

Like a Hole in the Head is a 1970 thriller love story novel by British writer James Hadley Chase.
Plot summary.
Ace marksman Jay Benson lives a retired life from the army with his beloved wife Lucy, and starts a school for training in firearm shooting. Unfortunately they fall short of money, when Augusto Savanto walks into their lives, promising Jay a huge sum of money in return for teaching his son Timoteo, who is totally uninterested in shooting. He wants his son to be able to shoot like an expert in just nine days. Benson agrees but soon realizes that he has entered a circle of revenge and murders involving mafias, in which he must participate, else it could affect both Lucy and him.