This is another great "Reacher" book. This book is actually the prequel or rather what should have been the 1st book in the series. This is the last time he is in the army before he starts his wanderings. It shows how he actually came to live like he does.
Anyway, he is sent to investigate a murder in rural Mississippi. His job is to blend in with the locals and try to find out what happened. Above all, though, he is to let the army know if the murderer is a soldier stationed in the town. Or rather to protect the army above all costs, because of course, the base is the site of very top secret missions. Very good as always.