Any examples of excellent 'blurb' that made you buy a book?
"WHAT IF you could go back in time and change the course of history? WHAT IF the watershed moment you could change was the JFK assassination? 11/22/63, the date that Kennedy was shot - unless . . ."
I think it's because in just a couple of lines he's summarised the whole plot and got over a sense of how intriguing an answer to the what-if's could be.