I've read very few of King's novels - just this, Dolores Claiborne, The Stand, and Different Seasons - but I consider myself a fan because I love his non-fiction On Writing and his magazine work. While there were things I liked about this book (after all, I did read all 850 pages), in the long run, I was disappointed.
This was about Jake, who gets the privilege?/duty? to travel back in time to alter history by preventing the assassination of JFK. I liked the early part of the time travel when Jake is in Maine and the history-altering he does there, and then the relationship between Jake/George and Sadie. Could you read this book and not love Sadie? (The answer is no.) Other than that, I didn't like too much. I found everything about Oswald pretty non-engaging and it seemed I read an awful lot about apartment complexes in 1960's Texas. (Now Oswald lived here, now Jake/George moved there, and on and on and on...) The inherent complexities in time travel weren't handled either particularly well or innovatively. And there were three ends: the end of the "mission" (so to speak), the end of the after-mission, and the very end (sorry to be so cryptic; I don't want to be a spoiler). The after-mission piece - where the results of everything that's come before were revealed - was utterly and laughably ridiculous. Why would any of those things have happened? However, I did like the very end/coda.