In early 2002, Stephen King said he was written out and was thinking of retiring. Some retirement. He has since published at least four novels, a couple of story collections and has collaborated on a monthly comic book. On Wednesday, Scribner, his publisher, announced that in the fall it will bring out yet another King novel, called “11/23/63.”

The new book is 1,000 pages long — enormous by most standards, but cruising length for Mr. King — and is apparently a “counterfactual,” a novel that imagines what would have happened had history turned out differently. It’s the story of a Maine high school teacher named Jake Epping who discovers a portal back to 1958 in a storeroom at a local diner. He travels back there and, while enjoying some sex and rock ‘n’ roll, finds himself with a chance to thwart the assassination of John F. Kennedy....