Philip K Dick 
Penultimate Truth 

A masterly tale of political deception from the most significant SF writer of the 20th century World War III is raging – or so the millions of people crammed in their underground tanks believe. For fiteen years, subterranean humanity has been fed on daily broadcasts of a never-ending nuclear destruction, sustained by a belief in the all powerful Protector. Now someone has gone to the surface and found no destruction, no war. The authorities have been telling a massive lie. Now the search begins to find out why.