Warfighting is an invaluable resource for anyone interested in the subject. Currently on the USMC Commandants' professional reading list.
Leading Marines (Unabridged)
Infantry in Battle (Unabridged)
The Warrior Ethos (Unabridged)
Chesty: The Story of Lieutenant General Lewis B. Puller, USMC
The Marine Corps Way: Using Maneuver Warfare to Lead a Winning Organization
Fields of Fire