Milla, Carlos. Genesis de la Cultura Andina, 4th ed. Cusco: Amaru Wayra, 2006. If you can read Spanish, this book presents esoteric theories based on many of Peru’s ancient ceremonial centers. Milla’s latest book, 2003’s Ayni: Semiotica Andina de los Espacios Sagrados, from the same publisher, focuses on astrology. Carlos Milla can be reached in Cusco  at cmilla [at] viabcp [dot] com.
Villoldo, Alberto, and Erik Jendresen. The Four Winds: A Shaman’s Odyssey into the Amazon. New York: Harper Collins, 1991. Even Peru’s shamans respect this work, which documents the author’s spiritual initiation into Amazon rituals.