Just finished reading 11/22/63, Stephen King's contribution to the ever-developing legend of the JFK assassination. For those of you unfamiliar with the novel, it focuses on Jake Epping, who travels back in time from 2011 to the late 1950's, with the intention of preventing Lee Harvey Oswald from assassinating JFK. For those of you unfamiliar with the story of the Kennedy assassination, I can't help you--although I will suggest that King's novel provides a better primer than Oliver Stone's conspiracy-happy "JFK."
I highly recommend the book: It's one of King's trademark tomes--nearly 850 pages long--that you can just get lost in for hours on end. What makes the book special, though, is it's unpredictability. That is, even if you assume that King will ultimately provide a relatively happy ending (for all that he deals in horror, his novels are seldom tragic), in this particular novel, you cannot be sure what a happy ending is. Do we want Jake to prevent Kennedy's assassination? Will that make the world better or worse?
Far be it from me to answer that question: Read the book yourself to find out.