Rupert Smith's "The Utility of Force" or Col. Hammes' "The Sling and the Stone" for a historical overview for how we got to where we are. I believe the latter is more readable.
For historical context, Mao's "On Guerrilla Warfare" (the Griffith translation is preferred) is a seminal work.
LtCol. Nagl's "Learning to eat soup with a knife" is a more academic piece comparing the successful British COIN campaign with the failed US campaign in Vietnam.
Regarding Iraq, Hashim's "Insurgency and Counter-Insurgency in Iraq" is a good, comprehensive examination of the makeup of the Iraqi insurgency.
Bard O'Neill's "Insurgency and Terrorism" is a good general dissection of insurgencies.
Gil Merom's "How Democracies lose Small Wars" is an interesting look at the difficulties democracies have in pursuing protracted, limited conflicts.
Once you get into history of specific conflicts, the possibilities are endless.
Bookmarks