“How many books have been written about the chain of events leading up to that day in Dallas?” wonders Jake Epping, narrator of Stephen King’s 11/22/63. “A hundred? Three hundred? Probably closer to a thousand.”

Undeterred, King has written a big, page-turning novel that explores the events culminating in President John F. Kennedy’s assassination through the eyes of Jake, a 35-year-old high schoolteacher from 2011 Maine able to travel back through time — and potentially save Kennedy’s life.

Jake’s rabbit hole into the past originates in the pantry of a greasy-spoon diner owned by Jake’s buddy, Al Templeton.

On the other side of the great divide?

The same Maine town that’s been left behind, except now it’s just before noon on 9 September 1958.

A long-closed paper mill is humming with life. A large root beer from an old-fashioned soda fountain costs a dime. Five gallons of gasoline goes for less than a buck. Everybody smokes. Nobody uses computers.

After spending a dazed half-hour in what he calls the Long Ago, Jake steps back into 2011. Al, who has eagerly been waiting for Jake’s return, explains how this passage to the past works.

No matter how long one is gone, only two minutes lapse in 2011, although the time traveler continues to age by the same amount of time spent living in the past.

Every time one steps back from the present into 1958, there is a reset, wiping out what was changed by one’s last visit.

Dying of cancer, Al wants Jake to go back and finish off what he himself is now too sick to do: Hang around the past long enough to murder Lee Harvey Oswald and stop Kennedy from being killed.

“Save Kennedy, save his brother,” Al pleads. “Save Martin Luther King. Stop the race riots. Stop Vietnam, maybe. Get rid of one wretched waif,” continues Al, referring to Oswald, “and you could save millions of lives.”

It’s no accident that King’s first exercise in such counterfactual history involves the five-year period leading up to Kennedy’s death. We’ve been down this road with him before.

Set in 1960, King’s “The Body” (1982) describes the special bond between 12-year-old Gordie Lachance and his friends, for whom innocence quickly gives way to experience during the trip in which Gordie sees his first dead human being.

Also set in 1960, King’s “Low Men in Yellow Coats” (1999) describes 11-year-old Bobby Garfield’s own loss of innocence in a world both more beautiful and more evil than he had ever imagined.

Elected in 1960, Kennedy too takes us back to the seeming innocence of a time when anything seemed possible — before baby boomers like the 64-year-old King had grown up, leaving youth and its wide-open dreams behind.

“We had an opportunity to change everything,” laments a character in King’s “Why We’re in Vietnam” (1999), a story that looks back with regret at how little the baby boomers accomplished.

Saving Kennedy’s life dangles the promise of a second chance.

Recently divorced and drifting, Jake warms to the idea that he can irrevocably change history. Before long, he has been reborn as George Amberson, counting down from 1958 to his date with destiny.

King’s novel doesn’t pull punches in detailing what was wrong in the Camelot of his youth, from racial hatred and legal segregation to unchallenged sexism and routinely battered women.

An early detour to Derry, Maine — that fictionalized cesspool from King’s novel It (1986) that had been rocked by a series of grisly murders in 1957 — sets up parallels with an equally noxious Dallas, a city that King pummels in this novel.

But Jake nevertheless falls in love with a world that not only features rock-bottom prices, but also manners, World Series games played in the afternoon and people routinely watching out for and helping one another.

It doesn’t take long before Jake also falls in love with someone from this world: Sadie Dunhill, school librarian in Jodie, the small Texas town where Jake teaches English in the early ‘60s.

King doesn’t rush, taking a long timeout from his overarching narrative conceit and the inexorable march of history to bring alive this vanished past and Jake’s once-in-a-lifetime love story.

Jake reaches a point where he frankly admits caring more for the world he has entered than the one he left — and caring more about Sadie and his students than about Oswald and JFK.

So do we, which makes for some long stretches, as Jake pulls us away from Jodie so that he can resume his cloak-and-dagger efforts to determine whether Oswald acted alone.

As Jake rightly recognizes, Oswald is a punk, and even a master storyteller like King can’t make him — or the contrived plot twists through which Jake eventually concludes there was no conspiracy — very compelling.

But as Kennedy’s trip to Dallas grows closer, the pace of the novel quickens, culminating in a great set piece that it wouldn’t be fair to disclose.

Along the way, Jake wrestles with a question that first dogs him before he leaves 2011 and then persists into the novel’s final ingenious pages: “What if I managed, God knows, to stop it from happening and made things worse instead of better?”

Two related questions hover, just out of view.

In imagining he has the right to kill another so that he can single-handedly change history, how different is Jake from the fanatical Oswald, who killed Kennedy to bolster his customized view of the world?

And what right do any of us have to change others’ stories in order to write our own?

King has been asking versions of both questions for a long time.

King has always been acutely aware of the demented forces — from the Crimson King to Big Jim Rennie — trying to shape history to fit their master narrative.

And he always has sided with the little guys who fight back, trying to disrupt that narrative’s flow.

Jake may wear a similarly white hat, but his efforts to rewrite the past in his own image also dabble in black magic, of the sort that tempts every great quester searching to write the story of a different and better future.

As 11/22/63 proves anew, King is one of them, and his latest quest merits a journey of your own to your favorite bookstore.