This is my 2nd book which is a US president assassination spin off.
This should be the next Butterfly effect movie. It combines the "back to the future" theme with a final destination concept.
The past is obdurate. It resist change. This concept makes changing the past a bit harder than what we usually see from the same type of movies. The bigger the change you want, the stronger the resistance you will get in your attempt to change the past.
A great read from the great stephen king combined with historical facts about the JFK assassination.