What is the 13th valley about?

The 13th Valley by John M Del Vecchio is about Operation Texas Star, in which the US 101st Airborne and the ARVN (Army of the Republic of Vietnam) were airlifted into the Khe Ta Laou Valley in the A Shau area of operations. More specifically, the book focuses on several soldiers in an infantry company of the 502nd Regiment, culminating in the battle of Fire Support Base Ripcord.