Future Shock was the title of a seminal work by Alvin Toffler in the late sixties, in which he prophesied a number of sociological changes that would arise as a result of new technologies and changes in the workplace then happening. The term has since come to be used for any scenario which illustrates such an event or change where the hitherto unthinkable or unimaginable occurs in real life. Science fiction once might have been considered future shock, of course, but today many of the settings in science fiction predict a change or take place in a setting we might expect, such as the colonisation of Mars. Similarly, not all future shock is science fiction: some future shock scenarios may describe geopolitical events, such as the breakdown of the USA or Russia.
Although the term is a relatively new one, the idea is not. H G Wells may be considered an exponent of future shock when he wrote War in the Air, a little-known work which before the First World War depicted the use of aerial bombing and atomic weapons which ultimately pitched mankind back into a new Dark Ages. Similarly George Orwell's 1984, written shortly after the Second World War, may be considered future shock, although it might also come under the heading of dystopian vision.
Nature's End, Strieber and Kunetka.
The Drowned World, J G Ballard
Two novels on the Megalodon
Vortex, an alternative ending to apartheid in South Africa.
Cauldron, a future war in Europe without NATO or the EC.
Darkest Days, a modern day escalation into a world of conflict and the emasculation of democracy.