11/22/63 :: Countdown to Halloween 2013
11/22/63 is excellent read and one of my all time Stephen King favorites. But of course I am a big fan of the concept of time travel and multiple universes (hence my enjoyment of the Dark Tower series).
I actually read this one last year, having borrowed it from the local library. I picked up this hardcover copy to give to my sister (the previously alluded to horror fan) as a birthday present.