This is a classic book about the psychedelic experience, especially the
first essay. Huxley brought years of interest in the mystical experience with him to his drug experiences and was a respected writer.
There is a collection of his writings on psychedelics and drugs in general called
Moksha: Aldous Huxley's Classic Writings on Psychedelics and the Visionary Experience, edited by Michael Horowitz and Cynthia Palmer, which is well worth reading.