At the moment I am reading Penny Thornton's The Forces of Destiny, Incarnation, Karma, and Astrology, it is an interesting read, there isn't too much astrology, but lots of thought provoking information on how Fate and Destiny play out in our lives. Here is a quote from the book as an example of it's content:

When I took the diploma of the Faculty of Astrological Studies, I had to discuss in an essay the dilemma between fate and free will. At the time, the issues appeared quite cut and dried to me that while there was a divine plan at work, we also had the God-given ability to exercise free-will. I find the issue much more complex now. As an astrologer, one cannot avoid the knotty problem of fate, since a birth chart at almost every level is showing a fated pattern, even if character is the fundamental issue and future 'trends' are avoided; character may indeed be destiny, but how did we come to have such a character in the first place? Is this not also fate? And where does free will come in when the individual is born with deformities or multiple disabilities?

I am a quarter of the way through the book, there is talk of planetary spheres in chapter 4. Edgar Cayce discussed this in his 'sleeping states', and here is a link to this information, and also here in the index you will see Astrology.