I'm in the middle of it now. It's one guy's (Carlos Castaneda) recounts of Don Juan's teachings on Mescalito (peyote), Jimson's Weed, and others. It goes into depth about the collection of the plants, the preperation/ritual phase, and Carlos delves very deeply into his personal accounts with the substances. It really focuses around Mescalito, the actual BEING they frequently encounter while on peyote. It's a pretty interesting read to be honest with you. A lot of members on this board will appreciate it.
i read the teachings of don juan, the lessons of don juan, and i am halfway through A Separate Reality. They really are eye opening and insightful, and were a great read for me while a i simultaneously experimented with psychedelics for the first time. it really shows the necessity to never assume we know all there is to reality, as well as the care we must take to live correctly, especially when dealing with higher forces.