Susskind describes the decades-long battle between the quantum mechanics community and the general relativists as to whether information is lost when objects pass through the event horizon of a black hole and the hole eventually evaporates. According to Prof. Hawking and the GR community, as nothing can ever reappear from inside an event horizon, the information is indeed totally lost.

Susskind and Gerard 't Hooft begged to differ. Loss of information would violate the basic time-reversibility of QM: Hawking's ideas would lead to universe-destroying phenomena (p. 23). Somehow, the information locked the wrong side of the event horizon must leak out via Hawking radiation. But how?

The resolution of this dilemma took many years of conjectures and refutations. Susskind takes us on a tour of entropy, holographic principles and physics at the Planck scale. And the adversarial plot keeps the reader turning the pages.

I am normally very dubious about popularisations. They proceed by raking up endless analogies which never quite fit together, so that by the end of the book, your mind is like that jig-saw puzzle you bought and could never fit together.

This book was never going to be the exception - the mathematics of quantum field theory, general relativity and string theory are just too arcane for popular culture concepts to cohere around. However, there are wonderful insights all the way through this book and we do end up learning something about the large scale map of the territory. Apparently even the experts find it hard to get the whole thing into one focus.