This storyline was definitely more up my alley. It's a story of time travel with the idea being if you could go back in time and save JFK from being assassinated would you, and if you did what would the ramifications be.
Overall I liked it. Jake Epping is an English teacher in Maine (of course, this is Stephen King) is told of a passageway back in time from the owner of a local diner named Al. The passageway is in his pantry and this one always brings the time traveler to an abandoned mill from 1958. No matter how long you spend in the past only 2 minutes passes in the real world. Jake takes a quick trip back the first time, and then agrees to go back for a longer stint to prevent the Kennedy assassination. Both Jake and Al are aware of the butterfly effect but feel that the potential benefits of saving JFK outweigh those risks. They feel that if JFK lives so would Bobby Kennedy and Martin Luther King Jr. If MLK lived, their theory is there wold be no race riots, etc. A snowball of wonderful peaceful times. Sounds good in theory, but as Jake soon learns the past is obdurate - it doesn't want to be changed. Little things are no big deal but the more he tries to interfere with watershed moments in other peoples lives (and he handles a couple of personal things before getting to JFK), the harder it is.
Since he has to spend sometime in the past before getting to 1963, he does develop relationships with people in the past and tries hard to keep the truth of where he came from as well as why he is there secret, but as time goes on and relationships deepen that gets harder.
I won't ruin the ending, but I will say I enjoyed the book and was satisfied with ending.