The basic idea, if you don't already know, is that you can go back in time and save JFK. Of course, it doesn't go well. No spoiler there, if you visited the book's website or, you know, ever picked up one of his other book.
The basic run down is this: high school English teacher gets roped into the plan to save JFK by an acquaintance. The acquaintance is a diner owner named Al whose pantry is a rabbit hole (King's phrase) into September 1958. Same time, same place, every trip. Each trip is a reset. Al's changed a few things to see if it's possible, but decides it's time for something big. No matter how long you stay in the past, you're only gone from 2011 for two minutes.
Al attempts to save Kennedy, but has to come back before November 1963 because he is diagnosed with lung cancer. The dying man looks to the English teacher to take up the mission. The teacher tests out the idea, and finally agrees.
