US MACV-SOG Reconnaissance Team in Vietnam (Warrior, 159)

This is part of that Osprey series that covers everything about war, so if you know the series, you get the general idea. This book covers training, equipment, and tactics in the most detail, operations a little bit, and the strategy and politics of black ops not at all.

That said, the most interesting parts are how soldiers joined MACV-SOG (it involved going AWOL and tracking down one of the secret HQs), and the massive personal firepower used by small teams to fight and survive behind enemy lines and out of the range of air support.