This is book 22 of the "Jack Reacher" series.

This note does not contain major spoilers for the book.

Jack chooses to get involved; it's kind of the key to these books. For some reason he can't make commitments in a planned or controlled way, but he can commit himself totally to finding something out or fixing something.

In this case, what sets him off is finding a West Point class ring in a pawn shop. This leads him to the most beautiful woman in the army, who had her face blown off in Afghanistan, and now has to get pain meds informally since the system isn't doing a decent job.

I guess you could call it an "opioid epidemic" book, but it's ahrder to call whether it's pro or anti. They clean up a bunch of trouble along the way, and then he wanders off again.