If there were only one book that I would recommend on the subject of understanding consciousness and the development and levels of consciousness, then this would be it. If I were to take a million people and start a new civilization on a planet in a galaxy far, far away, and if I could only take one book with me, this would be it.
In reading the first chapter, I started to have my doubts about whether I should take the author seriously. The stories told stretched my credulity, to say the least. But this did not detract from what I got from that first chapter, or from the rest of the book. What came out of this is a treatment of the levels and development of consciousness that is so comprehensive and so thorough, and so extraordinary, that it is hard to imagine that anything could improve on it.
Wade describes 8 levels of consciousness, starting with a primordial, blissful womb-like consciousness, then the rude awakening of entering the world, then the steady climb (or at least conceptually steady) through higher and higher levels ending with an experience of Unity which includes even the previous seven states in what is a state which few if any have fully achieved, but which we all have an inkling of, otherwise we would not even be able to understand the last chapters. If you are into the Vedas, or Charles Tart, or Ken Wilbur, Peter Ouspensky, Maharishi Mahesh Yogi, etc., etc., then you will find here a book that really puts it all together, such that one has a feeling that absolutely nothing is left out.