The population of Melbourne, on the southern coast of Australia, has a few month's grace before the deadly radiation fallout from a nuclear war in the northern hemisphere reaches them.
The story is set in 1963, which is a few years later than when the book was written, and so presumably reflects the fears at the time that a nuclear war was very close, and that it would be inevitable that radioactive fallout would cover the earth. I suppose that these days the plot would incorporate global warming, or oil depletion.
But the scenario was very plausible - WW3 having involved Russia and China, with the US being dragged in and "cobalt bombs" being used everywhere. The Australians feel somewhat aggrieved that even though they took no part in the war, they have to face the consequences, albeit a couple of months later.
I remember reading an Asimov short story, where (IIRC) everyone on earth dreamed one night that the world was to end the next day, and they all believed it to be true. But on the last day, everyone carried on his/her business as normal - and that's how the characters in the book, for the most part, behave. There's no anarchy, or mass "giving up": people carry on going to work, having social evenings, shopping. This seemed fairly believable, although I wonder whether it might have been more realistic to assume that some people would try and migrate further and further south in an attempt to out-run the radiation cloud. No-one seemed to doubt that it would arrive and kill them; I'd have thought that there would be many who would be in denial, or cling to the hope that if they eluded it for long enough it would run out of power.
That's not to say they ignore completely the coming threat - the authorities make provision for suicide pills, and as the end gets nearer, they bring forward the dates of the fishing season and Grand Prix to allow people to enjoy themselves, but on the whole people operate on a kind of double-level: knowing that the end is coming, but determined to carry on as normal.
This is most evident for Dwight, one of the main characters, who's the captain of a US submarine, which is the last remaining vessel of the US Navy (or any US force I suppose). With the support of the vestigial Australian government, they arrange a voyage across the pacific and up the west coast of America, to reach Seattle. That's because they are receiving strange radio broadcasts from that area, and they want to investigate. It's believed very unlikely that anyone is still alive, but the mission is carried out under the same conditions as if it had been peace-time. And so Dwight and his crew, including some Australians, follow their duty and spend over a month at sea, rather than making the most of their limited time on shore with their families.
I did feel very convinced by the book, and had a couple of confusing times when walking around town after having been listening to it in the car - I found myself thinking "yes, it's true: people are just carrying on as normal!".
The whole thing was done very well - moving and powerful. The ending was especially good.
Completed : 07-Oct-2011 (audiobook)