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.
Before I read any of CC's (33!) work in my youthful prime, I once foolishly ingested Datura during a psylocybin mushrooms trip.
Everything around me turned blood-red, my vision was seeing the world in shades of blood-red only.
Imagine my surprise several years later, when reading CC and he quoted Don Juan's explanation on Datura, stating that the spirit living in this particular plant medicine was very powerful but also dangerous:
If your vision turned red, it meant the spirit had accepted teaching you. If everything turned black, you were dead.
I am a firm believer in the truthfulness of Don Juan's existence since then...