Definitely Slaughterhouse-5 and Timequake. Timequake has to be one of the smartest premises for a book EVER...
The idea is that the universe stops expanding for a nanosecond, sending everyone back ten years in time. The catch is that you are aware of the glitch and must live out your life exactly as you did at the time, only now you have no freewill. Thus, if you are about to do something you will regret (suicide, murder, break up etc) you are obliged to behave exactly as you did, even though yo wish to erase your mistakes. Everyone is the same. Without freewill, mankind is trapped inside their own consciousnes and forced to behave almost like robots, prisoners of their pre-programmed histories... Great book. Also, try Cat's Cradle - another great (and short) book about a new way of changing the properties of water so that a single drop can freeze an ocean. It's a biting satire on weapons of mass destruction.