The greatest true-crime story in music history, as only James Patterson can tell it.

With the Beatles, John Lennon surpasses his youthful dreams, achieving a level of superstardom that defies classification. "We were the best bloody band there was," he says. "There was nobody to touch us." Nobody except the original nowhere man, Mark David Chapman. Chapman once worshipped his idols from afar—but now harbors grudges against those, like Lennon, whom he feels betrayed him. He's convinced Lennon has misled fans with his message of hope and peace. And Chapman's not staying away any longer.

By the summer of 1980, Lennon is recording new music for the first time in years, energized and ready for it to be "(Just Like) Starting Over." He can't wait to show the world what he will do.

Neither can Chapman, who quits his security job and boards a flight to New York, a handgun and bullets stowed in his luggage.

The greatest...