Richard de Mille demonstrated that Castaneda's work was a hoax. He lifted entire passages from other authors such as C.S. Lewis. The Indian tribe that he supposedly apprenticed under never used peyote.
If you think you can master his material and jump off a cliff and survive as he claimed to do, please do so.
Are you asking about Carlos Castaneda's works and his followers specifically, or New Age?
As for New Age, here is a paraphrase of a good summary of the "movement":
“New Age religion” is perhaps a better term.
New Age is often a response to people's religious questions and needs, and its appeal is to people who are trying to discover or rediscover a spiritual dimension in their life.
Many within the New Age movement themselves distinguish carefully between “religion” and “spirituality”. Many have rejected organised religion, because in their judgement it has failed to answer their needs, and for precisely this reason they have looked elsewhere to find “spirituality”.
Furthermore, at the heart of New Age is the belief that the time for particular religions is over, so to refer to it as a religion would run counter to its own self-understanding.