Maybe you´d be interested in reading Huxley´s "The Doors of Perception", where he describes much of his experiences (under medical control) with hallucinogenic mushrooms. There was a second part to be written, which unfortunately was lost because of one of those fiery fires in California, which burned all the documents, but this one is more than worth reading...
And later, you could search for some documentary books describing the whole ceremony of collecting peyotl in New Mexico, which are most interesting: this is an almost millennary practice, with strict rules, and done in a very special spiritual condition...
About altered states of consciousness, simply google on those words, and you can spend a very rewarding time reading some very interesting things...
Regards
BF