Lennon and Ono’s longtime friend Elliot Mintz writes about their marriage in his new book ‘We All Shine On: John, Yoko & Me’

A new book about John Lennon and Yoko Ono gives an inside look at the marriage of one of rock and roll’s most intriguing couples.

Written by the rock-star couple’s close friend Elliot Mintz, We All Shine On: John, Yoko & Me (out now) illustrates that while Lennon and Ono were deeply connected, they also weathered times of discord.

The book recounts a story from 1972, when Lennon and Ono were guests at a party where the former Beatles singer got drunk while watching the presidential election results between Richard Nixon and George McGovern at anti-war activist Jerry Rubin’s Greenwich Village apartment.

As it became clear that Nixon would win by a landslide, the mood grew grim, writes Mintz. And as his drinking got heavier, Lennon ended up having “loud, raucous sex,” with another woman at the party.

John Lennon and Yoko Ono in 1980.Jack Mitchell/Getty

“Throughout it all,” Mintz writes in We All Shine On, “Yoko sat on the sofa, in stunned, mortified silence, as other guests began awkwardly getting up to leave — until they realized that their coats were in the bedroom where John was having sex.”

Looking back, “He was placing [his wife] in the most embarrassing position that you could ever place a woman in — having a romp in the hay in another room with thin walls while your wife was attending a small party and could hear everything,” Mintz, 79, tells PEOPLE exclusively. “Yoko is a very stoic woman, but it would have severe consequences.”

The next morning, Mintz got a call from a very hungover Lennon, who had to sleep on the sofa that night — and Ono, with whom he remains extremely close to this day, would later tell him even more.

John Lennon and Yoko Ono with their friend, author Elliot Mintz.Courtesy of Elliot Mintz

Mintz says that Ono told him, “I can forgive him, but I don’t know if I can ever forget what happened. I don’t know if it will ever be the same.”

“The reality is,” reflects Mintz, “as I would learn over the years in the bad behavior department, John would say to me, ‘Ellie,’ which is what he called me, ‘I’m not always the ‘Imagine’ guy.’”

Lennon was murdered on Dec. 8, 1980.

‘We All Shine On: John, Yoko, but & Me’ book cover art (by Elliot Mintz).Dutton

Nearly 44 years later, Mintz says, “Don’t get me wrong. Much of the time, he was the person that we related to, who wrote ‘Imagine’ and expressed his vision of the kind of world where we would all like to live. But he didn’t always stay there. He was imperfect.”

Adds Mintz, “It’s one of the reasons, by the way, we all fell in love with him — because he was real.”