Sadly, the book immediately starts off by saying "Why" is not as interesting as "How" and goes on to make fun of theologists for never agreeing on the definition of "nothing" -- which is certainly true as far as it goes, but still doesn't address the actual teleological problem.

What he does do effectively is discuss the various physical phenomena underlying "nothing" -- virtual particles, quantum foam lattices and the Higgs field. He goes write back to the Big Bang and points out the quantum fluctuations at the point of Big Bang expansion could have "created" energy in the sense that the total energy is zero, but getting to the resting zero state is effectively impossible.

I felt a bit cheated after reading Brian Greene and Three Roads to Quantum Gravity, but he does get to the essential point that the Big Bang may have happened because "quantum nothingness" is unstable, but it still doesn't get to the question of why or how "nothing" can be "unstable" at all. Oh well.