One of the hundred books a year I read:

This is the 24th and last Jack Reacher book written solely by Lee Child who is passing the franchise to his son.

Reacher steps off a bus to prevent a mugging of an elderly man. When he discovers the man has a large sum of cash to pay off a loanshark, Reacher decides to accompany him to make sure everything goes smoothly. Of course, it doesn’t.

The two organized crime groups controlling the city have a long-standing truce business in half. One gang initiates a double-cross that shifts the loanshark operation from one group to the other. The elderly man Reacher has decided to protect is caught in the middle and that offends Reacher’s sensibilities.

Like most Reacher books, the bad guys can’t figure out who is messing with them. The best part of this one is each gang is convinced that all the bad things that happen must be caused by the other gang which creates this ever-increasing overreaction to events. The body count, of course, is going to be high.