The Affair - Lee Child

The Affair is a Jack Reacher Novel. While this is novel 16 in the series, it's actually the story of Reacher's last official assignment, and why he left the army.

Jack Reacher is a major in the U.S. Army. Reacher is an MP who's been assigned to help keep a civilian investigation, into a murder outside an army base, from spilling over onto the soldiers on the base. What Reacher does is the right thing, not necessarily what the army wants. This is an excellent book and a great edition to the Reacher series. Very highly recommended.