This is, however, a very odd little (about 200 pages) book. The author is a "doctor of Oriental and naturopathic medicine" and has been spending much of his career hanging about various Native American tribal groups investigating their healing techniques. This book would have benefited greatly had he also picked up an editor somewhere along the way! The Andean Codex, while fascinating in some of its details, varies widely in tone and focus, occasionally threatening to veer off into Newage blithering, and frequently descending to "typing up the journal" levels of mundane minutia.
The book starts off in the Amazon, with the author (and some other introduced, then dropped, characters) experiencing Ayahuasca. The jungle Shaman says that Williams has had such a powerful experience (uh-huh) that he has to go to the Andes to work it all out (???). The next chapter starts a few years later, he's returning to Peru, and is doing the necessary tourist trip up to Machu Picchu, where he runs into a "world peace" event featuring three Tibetan lamas and three Q'ero shamans. Oddly enough, nobody organizing this seems to have provided for translation, so he steps in to conveniently provide a Spanish-English bridge between the Shaman that conveniently speaks some Spanish and the Lama that conveniently speaks some English. Once again, characters are introduced, developed, and dropped. He ends up waiting for a train (without reservations) with the Q'ero (who conveniently do have tickets "but don't know what they are"), and they all eventually get back to Cuzco, and he starts working with them over the next several years. Again, the "convenience" of the various events described begs the reader's "suspension of disbelief" beyond what most books would (even of the "shamanic genre"), and generally sets one's "B.S. detectors" into full alert.
This is not helped by the oddest part of the book, when he does a seemingly pointless (and very "Newagey") story of when he was on a pilgrimage to Mt. Shasta back in the 70's, and "miraculously" finds the Shasta Abbey and is seen by some holy lady who has been in solitary retreat (and "doesn't see anybody" but sees him because she's "been waiting for him" ... uh-huh) who relates a story about an expedition to the fabled lost Incan city of Paititi, while naming folks that one would assume would have a function in the over-all context of the book. Again, characters and plot lines are developed and then discarded, with only the idea "looking for Paititi" (discussed with the Q'ero) resurfacing later.
Eventually, the Q'ero have him come up to their high-mountain land, and he gets terribly altitude sick and nearly dies (here is where he sounds like he's just regurgitating his journals about what hurt, what he ate/drank, how he slept, etc.). He survives, and in the last chapter returns to the Amazon. Huh? Obviously, there is something to be said about non-linear narratives, but the book reads more like this is due to editorial abandonment rather than stylistic intent!
Now, there is useful material in this book, although the "Codex" of the title can be pretty much reduced down to a handful of "ethical principles" ... these are: munay, "lovingkindness/beauty", yachay, "correct knowledge", llank'ay, "right action", kawsay, "respect for life processes", and ayni, "reciprocity". While spun out in various stories and examples, this hardly compromises a "codex", and this would have been a much better book had the intent of making "a book representing Andean spiritual life" been focused on without the other (self-congratulatory) stuff!
As this is a relatively recent (especially for my collection) release, it does still appear to be in print, so were you so inclined, you should be able to find it at your local book store, but Amazon has it discounted a third off of cover, and their new/used vendors have "new" copies for about half of that. While I was interested in this for the look at the Q'ero, you likely are not operating with that connection, as such (unless you're hot for "Newagey" fluff), it is hard for me to recommend this largely incoherent book. As noted above, this could have been beaten into something of substance, but it's way too self-indulgent in the broad strokes and too cursory in the details to be something I'd tell just anybody to go pick up.