I'm still on Book 3. Book 3 is a tough read. Anyone who thinks that Jane Roberts "free-associated" this material ought to take a gander at this book. I can imagine Robert Butts patiently and somewhat bemusedly transcribing Seth's intricate discussions of atoms, inner and outer realities, idea construction, the existence of the physical body within multiple realities. You cannot make this stuff up. This will be a book that I will have to re-read (again) much later. However, Book 3 does introduce a seminal and (in my opinion) important idea: that an electrical counterpart to our physical universe exists "nearby." This electrical plane is the described as the closest non-physical reality to ours and in fact intermingles with the physical. Per Seth, our physical manifestation of electricity is a weak echo of the actual power of this reality; the electricity that we've managed to harness in our world is merely a shadow of the electrical realm. It is this realm that is the most immediate after-death state. Dreams are electrical in origin, and their electrical signature is "translated" into images that we recall as a dream.
I regard this as a significant idea because it is theoretically testable; unlike vague ideas of an "astral realm," the idea of an "electrical realm" is one that we can (somewhat) wrap our minds around; and it may explain a very some puzzling paranormal phenomena, one that I've experienced all my life: street lights (and other lights) turning off when I approach... As well as the frustrating problem that I had as a child of not being able to wear a mechanical watch without it dying. It also explains the apparent ease with which the newly dead and the earth-bound are able to record voices on our electrical equipment, turn on and off lights, radios, doorbells, fire alarms, and even, occasional, power televisions even when unplugged. A simple idea, to be sure, but one that I've never seen discussed anywhere else.