This book is somewhat of a companion to the book "The First Three Minutes" by Steven Weinberg. In that book, Weinberg describes the physical conditions of the universe in the three minutes after the big bang winked it into existence. Davies distills current quantum and cosmological thinking down into an understandable explanation of what are the likely end scenarios for the universe.

In general there are two main endings postulated for the universe. The first is that it will continue to expand and all energy concentrations will eventually be dissipated to achieve what is literally universal thermodynamic equilibrium. The second is that the universe will cease expanding and start to contract. Once the contraction starts it will accelerate until all matter, which is the entire universe, will contract down into a singularity of infinite density. At this point time and the laws of physics will no longer exist.

Which end scenario is the eventual result is based on the density of mass in the universe, less than a certain amount and it is universal expansion, more than a certain amount and contraction is certain. At this time, the amount of mass in the universe does not appear to be enough to force a contraction; however cosmologists are finding additional mass all the time.

Where Davies diverges from other authors writing in this area is in his discussions of ways to create new universes and how advanced species could literally use the creation of new universes to be immortal. It was a fascinating thought because it is based not on speculation but on the highest levels of current cosmological thought. That section alone made reading the entire book worthwhile.