Castaneda's works contain descriptions of paranormal or magical experiences, several psychological techniques, Toltec magic rituals, shamanism and experiences with psychoactive drugs (e.g. peyote). Carlos Castaneda's works have sold more than 8 million copies in 17 languages.

Interpretation and criticism (the Castaneda controversy)

Many critics doubt the existence of don Juan, citing inconsistencies in don Juan's personality across the books and in the sequence of events in the books. Many Castaneda supporters claim in turn that the very fact of handling awareness and perception accounts for this; and that the actual existence per se of don Juan is irrelevant, since the important matter is the theme that don Juan presents.

What is easily understood is the fact that the writing style changes greatly from the first to the last of the "don Juan" books. The Teachings of Don Juan is an anthropologist's journal containing a lot of seemingly irrelevant, non-fiction information. The quasi-journalistic or academic tone of the earliest books disappears definitively in Castaneda's fifth book, The Second Ring of Power. This book marks a significant change in the character of the series. In addition to introducing a large cast of new characters, the later Castaneda books present don Juan's shamanism in far greater complexity than in the earlier books. The Eagle's Gift (eighth book) is a novel-like work with specific characters on a journey towards what they call "Total Freedom", and where the words of don Juan seem more like those of a scientist. This could be the result of changes in the mind of Carlos Castaneda.

As Castaneda was very elusive, and because his works were taken up by young people at a time when mystical and shamanic traditions were in fashion, many professionals cast doubt on the authenticity of contents of his works. When he followed up The Teachings of Don Juan with a series of equally popular books, including A Separate Reality (1971), Journey to Ixtlan (1972), and Tales of Power (1975), even more questions were raised as to how much of his work was true anthropology and how much was his own creation.

Another way to read the books is as a sort of game, almost like a detective novel. Depending upon one's approach, they could be either accepted at face-value in their entirety, or discarded. Some of the material could be considered true, some fictional; and some of the events described probably appeared to be real at the time, but could be interpreted as hallucinations. It is up to the reader to decide.