If the doors of perception were cleansed everything would appear to man as it is, infinite.
, The Marriage of Heaven and Hell
Though I like a possible alternate title, "What Your D.A.R.E. Officer Doesn't Want You To Know," Aldous Huxley chose the now infamous name of this work, first published in 1954 from the line above. The book describes the psychedelic journey taken by the author after ingesting .4 grams of mescaline and provides a coherant account of the effects of psychedelics and presents a case for their responsible use.
According to Huxley, hallucinogens are a way to open up the human mind to new ways of seeing the world, to new ways of thinking, and to creative possibilities. Written before the prolific use of such drugs that led to many casualties in the late '60s and early '70s, such an account may seem a tad idealistic in hindsight, but a very powerful and convincing book, and one that I think should be read by anyone wishing to delve into enthogenic adventures. Many websites post the full text of the book, erowid.org maintains a copy just to name one, a simple websearch should get you what you need.