This short book introduces the subject of Godel's investigation into the distinction between 'intuitive' time and the 'formal' time used in science, in particular, Einstein's theory of relativity.
On the way, it discusses Godel's incompleteness theorems, and the positivist philosophical agenda for formalising mathematical proof.
It is, accordingly, not a particularly easy read, but the writing style is clear.
The main message of the book is that Godel proved that there exist solutions to Einstein's field equations which describe universes in which time does not exist and that the consequence for us is that our intuitive notion of time must be ideal (i.e. based only on our particular internal experience and not an actual feature of the physical universe ).
This is a shocking result which seems to have been swept under the carpet, Hawking himself attempted an unconvincing ad hoc 'fix' to the issue.
A reviewer below is wrong in stating the Godel universe is profoundly different to our own, in fact it is possible that we live in an expanding Godel universe
I found this to be a fascinating and thought provoking book with few faults other than the last chapter which is a bit of a crusade against philosophical detractors. I agree with a comment below that some knowledge of Godel's theorem and relativity will make the book easier to assimilate.