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It's been a celebratory couple of months for fans of Paul Simon, who wrapped up what he's implied could be his final North American tour this week in his hometown of Forest Hills, New York.

Not everyone who's crossed paths with the award-winning songwriter feels positive about the experience, though.

In his new book, "Never Say No To A Rock Star: In the Studio with Dylan, Sinatra, Jagger and More," former A&R Studios engineer and producer Glenn Berger, who worked with Simon on albums like 1975's "Still Crazy After All These Years," describes the singer as callous, unsympathetic and snobbish, according to the New York Post.

"Paul just didn't seem to care much about other human beings," writes Berger, who now works as a psychotherapist.

Berger depicts Simon as being competitive, as well, claiming he still has a recording from a studio session on which Simon talks openly about wanting the song he was tracking at the time to make a bigger splash than

"Bridge Over Troubled Water," which he cut with Art Garfunkel and released in 1970.

"He [Simon] pauses for a giggle," Berger writes, "then adds, 'I used to have a partner named Art Garfunkel, and this would mean so much to me if I could just show … that it was, it was all me!'"

In another section of the book, Berger recalls being present when Simon stopped by the studio while a then very anorexic Karen Carpenter was working on a disco album.

Rather than offer constructive criticism, Berger writes Simon said, "... in a voice that combined derision, snobbishness, concern, and alarm ... 'Karen, what are you doing? This stuff is awful!'"

(Berger rehashed the moment in a piece for the Huffington Post last month, where he wrote, "I saw her collapse in despair when Paul … told her that her new material was 'terrible,' and a 'big mistake.'")

In the book, Berger concedes that while the music wasn't Carpenter's best, Simon's "insensitivity was stunning."

Berger continues: "Karen never released that album during her lifetime. Within a few short years, she was dead."

Other rock icons Berger takes aim at include Bob Dylan, Mick Jagger, Frank Sinatra, Burt Bacharach, Bette Midler, and James Brown, all of whom Berger watched as they "performed their hit-making magic, honed their sound, strutted their stuff, bared their souls, and threw epic tantrums," according to Amazon's description of the tome.

Simon, meanwhile, has said may be through with the music industry for good.

"Showbiz doesn't hold any interest for me," he said in a recent interview with the New York Times.

"It's an act of courage to let go. I am going to see what happens if I let go," he explained, adding that success in music comes with a price.

"I've seen fame turn into absolute poison when I was a kid in the '60s," said Simon. "It killed Presley. It killed Lennon. It killed Michael Jackson. I've never known anyone to have gotten an enormous amount of fame who wasn't, at a minimum, confused by it and had a very hard time making decisions."

In addition to the musicians mentioned in the book, Berger has engineered and produced albums for Christina Aguilera, Fiona Apple, Rob Thomas and others.