This is Stephen King at his best, which is a relief after the disappointing "Under the Dome."
The novel deals with the perils of time travel, and the consequences of interfering in history. The protagonist, Jake Epping, is given the opportunity to prevent the Kennedy assassination, but there is a catch: the portal's entry point is fixed in 1958, which means Jake has a lot of time to fill. He does this by creating two lives for himself: one in Dallas-Fort Worth to keep an eye on Lee Harvey Oswald, and another as a high school English teacher in Jodie, Texas. Needless to say, this has its consequences as well, not the least of which is falling in love with a woman who'll be around 80 years old in 2011. And what about those other lives?
Besides being a first-rate thriller, "11/22/63" is also a meditation on meddling where you don't belong and the reach of unintended consequences. Ordinarily, I would discuss some of the flaws, but for this book I honestly can't think of one. I only hope King is careful about writers and directors when it comes time to make the film. (Personally, I vote for Frank Darabont.)
Don't let its 850 pages daunt you. You'll turn them all, and quickly.