Next fall, legendary musician Carly Simon will open up in a memoir about her years-long friendship with former First Lady Jacqueline Kennedy Onassis, PEOPLE can exclusively reveal.
The book, Touched by the Sun, is set to be published on Oct. 22, 2019, by Farrar, Straus and Giroux.
In a news release, the publisher described the forthcoming book as "an intimate, vulnerable, and insightful portrait of the bond that grew between two iconic and starkly different American women."
"When I first met Jackie, I didn't imagine we had that much in common much less expect her to become my book editor, confidant, protective mother figure, and mischievous pal," Simon said in a statement. "She arrived when I least expected to make a new friend and she stayed up until the time of her death."
While Simon's friendship with Onassis, who worked as a New York City book editor for the last two decades of her life, has not been a secret, Simon has never discussed it in detail.
Onassis was Simon's editor when Simon, an icon of '70s rock 'n' roll, began publishing children's books in the '80s and '90s. Her first memoir, Boys in the Trees, was published in 2015.
She and Onassis had "a chance encounter at a summer party on Martha's Vineyard [which] blossomed into an improbable but lasting friendship," according to the news release announcing Simon's new book.
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A 1995 Vanity Fair article described Simon as one of Onassis' "kindred spirits."
"She loved them because they were free spirits, unguarded and spontaneous - what she couldn't be," a source told the magazine at the time. The two were close until the end of Onassis' life. Days before she died in 1994, Simon arranged a lunch for her with documentarian Ken Burns, according to Town & Country.
Simon was one of the many luminaries who attended Onassis' funeral in N.Y.C.
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"I've missed her deeply and am reminded of her every day," Simon said in her statement on Monday. "In the last few years, I found myself doing what I've done with all the other things in my life that were too big to look at directly and too important to understand fully as they were happening: I put it down on paper. I found that writing about our time together was the only way to begin to know what she meant to me."
She continued: "Publicly, Jackie was important to all of us, but privately, out of the public eye, I loved her. I wanted to share my experience of her."