For me this book confirms Tim Leary's status as one of the greatest thinkers of the late 20th century. His visionary understanding of the nature of human consciousness and of the processes of evolution are revolutionary and astonishing. As with a lot of his work it curious combination of psychological terminology and tripped out hippy alternativism don't make this an easy read, but it's well worth persisting. For me his Eight Circuit Model of Consciousness is audacious and enlightened, although he introduces it here, he does not categorise it in ways that I have read elsewhere. A challenging but utterly fascinating read.
Another book going deep into the concept of 8 circuits of nervous system. And in this one, you'll get more than satisfactory glimpse of the topic. A number of tables, graphs and diagrams to illustrate the point is offered, and a number of points, ideas and philosophies are included in it too. A real food for freethinkers.
Circuits are presented from many different angles, so the more you know about them, the better picture can you conjure up about each of them. 8 circuits times 3 phases in each circuit equals 24 stages along the whole scale. They are all very closely described. Without revealing too much, I can only say that first four called terrestial, and second four called post-terrestial, could be imagined as harmonics or octaves upon each other. 1-5, 2-6, 3-7, 4-8. Linked together in concept, but in higher dimension.
This concept is one example of many different models of one particular concept called Levels of consciousness. To find out more about it, you can just google it and click on first wikipedia page from the results. There will be a number of them listed nicely one after another. Or google straight 8 circuits of nervous system, and you'll see.