In truth, theres very little doubt that the stories are largely untrue. Anyone who has read the Don Juan series can see that Don Juan completely changes as the books go on, plus the various temporal mistakes are too many to simply be bad editing. Thatgl said, I don't know how Castaneda made such errors as they are so bleedingly obvious; its like he wasn't making any effort in terms of pulling of a good con, or he honestly believed the truth of what he was writing- or it was all true. I think that he does have some good ideas, and the stories are interesting, but its tarnished by being false and, in many ways, very self referencial and mundane. For me, the initial interest was born from the fact that these were 'genuine' shamanic teachings, so the discrepancies in the writing really turned me off. Perhaps if he'd written the stories as a kind of parable then it would be more important to me personally. I've always liked the idea that Castaneda was trying to conceal the truth of himself as a means to spirtitual elevation, and did so with confusion and misrepresentation but thats a kind of childish view. If he had avoided the commune/cult life that he seemed to pursue, I feel he would have had more credibility. There is something odd about the fact that several of his 'friends' vanished in 1998, with one person being found dead half a decade later. Who knows what happened?
Myself, I think the stories are a front for something different. The stories of shamanism and use of hallucinogens seem tailored to present a certain occult teaching to a society that was just fully entering into psychedelic/entheogen use.
