Nicolas Shakespeare, the author of The Dancer Upstairs has an incredible article on his first meeting with Martiza Lecca. Lecca is the ballerina in whose apartment Shining Path leader Alerto Guzman was captured. The article is haunting and excellent, check it out.
Not a lot is available in English about Shining Path, and much of what is available is very academic. My sources in the world of terrorism scholarship say the definitive book on the movement is David Scott Palmer’s The Shining Path of Peru. I might have to put that on the to be read list.