Huxley's experience with mescaline was part of a carefully observed, scientific experiment. He was an ideal subject for exploring these subjective phenomena, since he was an accomplished writer who had "dinner table" acquaintance with the values and interests of science.
The results are a fascinating read, and available on the web, for example at:
http://www.acuteproof.com/aldous/As with any first person account of a subjective experience, the narrator brings pluses and minuses to the narrative.
On the plus side, Huxley has the background to see the essential unity among the source of his drug experience, meditation, hypnosis, spontaneous alterations of consciousness (now known to be experienced by about one third of the population), and schizophrenic break.
On the minus side, he colors his interpretations to favor his preconceived religious or metaphysical viewpoint. These views may account for the OP's admiration.
It is a valuable document. Ironically, in light of Mattshark's comments, it is not fairly read as a "pro-drug" screed. Above all else, it shows that drugs are simply superfluous: all that happens with mescaline happens without mescaline, too.
Finally, a defense of shamans.
Shamanism is an umbrella term covering a wide variety of practices pursued all over the world, having in common only respect for animal spirituality, attention to mystical experience, and that the shaman has a day job.
Drug use is not a necessary element of shamanism, nor is shamanism a necessary context for drug use. When drugs do show up in a shamanic culture, it may not be the shaman who is taking them. Drugs, among many other methods, may help the shaman to give the rest of the community a taste of what the shaman's own visions are like, reproducibly and "on demand" as it were.
The shaman himself or herself may simply have no need of drugs. Conversely, other people may not have the resources or interest in pursuing a shamanic lifestyle. So, in the very best imitation of modernity, the other people take a pill instead of doing the work.