First, to my physics friends, apologies for the likely sophomoric butchery that follows.
The book's about quantum mechanics, some relativity, some cosmology with lots of frosting and little cake. Nonetheless it's very filling and satisfying. That's because this book is written at a good level for me, namely simplistic, lots of analogies, smells of over-simplistic explanations.
Reading this, I'm made to think that my preferred mechanism for learning is successive passes through material, with ever greater granularity or "pressure" leaving big voids and bumps at first, but eventually smashing everything into flat comprehensibility at the end. Will I ever get there with quantum mechanics? Doubtful, frankly. I loved the description of the interference experiment, and the implication that, for small scales, it's the past we can control, while the future is unknowable; exactly the opposite of macroscopic causality. Can I have that right? It's mind bending.
Re-cracking this book (just because I had nothing else to read last night) coincided with a SciAm article on string theory that drew inductive conclusions from linear, imaginary and then quaternion mathematics, citing 16 dimensional numbers as the next step, and infinite universes as a consequence if it's true.
Since I believe in the manifest and miraculous fact that mathematics actually works to describe the universe in which we find ourselves, I accept the inference, and expect & hope that someday we'll prove these universes are out there. That's really cool.