To start this review it is worth noting when this book was first published - 1975.
At this time the young, adventurous, scientific minded Mckenna brothers recalled their voyage of discovery. Through the use of hallucinogens they experienced thoughtful insights into shamanism, schizophrenia, the holographic nature of nature, and finally and maybe most memorably - they formulated a mathematical principle using the I-Ching that maps the history of 'Novelty'.
A great read, that will lead the reader on a voyage of their own.
Further study: The Timewave theory has since been scrutinised by expert mathematians:
Matthew Watkins found errors in the theory:
John Sheliak worked with Watkins objection and found that the theory could be corrected, and indeed it became even more accurate!