On the Beach, by Nevil Shute

Not entirely realistic, but this 1957 novel is a depressing peek into those days of yesteryear when we all lived under threat of nuclear annihilation (and hey maybe those days are coming back, better than ever!). A nuclear war has killed the Northern Hemisphere, and as the airborne radiation slowly crosses the equatorial barrier, spreading further south, the various inhabitants of Melbourne slowly come to terms with the inevitable and do what seems best with their remaining months, weeks, days, and hours, as they lose contact with other cities in the southern hemisphere one by one. If you need a book that will grind down your your sense of hope, this will fit the bill nicely.