Fifty years ago, shortly after writing “Golf in the Kingdom” but long before the book became something of a cult classic, Bay Area author Michael Murphy met an unexpected fan of his work: John Brody.

Brodie, nearing the end of his long career as a San Francisco 49ers quarterback, invited Murphy to training camp. Murphy was an avid Brodie and 49ers fan, so he quickly accepted – and soon found himself on a larger quest to understand the “inner game” of activities beyond golf.

He and Brodie collaborated on a magazine article in which they explored the quarterback’s uncanny bond with his wide receivers and used language about “slowing down time” on the football field.

“It’s become a cliché, but at the time it was kind of new,” Murphy said in a phone interview this week. “It touched a nerve in people.”

Now, at 92, he speaks from a different perspective. “Golf in the Kingdom” long ago grew from a bizarre oddity into a cultural phenomenon, one of the best-selling fictional golf books of all time with over a million copies sold. Monday’s charity event at Harding Park — benefiting ITP International (Integral Transformative Practice), the nonprofit Murphy co-founded — will punctuate the book’s golden anniversary celebration.

His story of the mystical and spiritual allure of gambling, conveyed by a fictional Scottish sage/teacher named Shivas Irons, inspired a loyal following. Murphy wrote about a young American stopping off in Scotland on his way to study in India – in real life he practiced meditation there for 18 months in the mid-1950s – and how his part of golf and his deep conversations with Shivas Irons open his consciousness and stir his soul.

Murphy is a Northern Californian at heart: born and raised in Salinas, educated at Stanford, and a longtime resident of Marin County. He also co-founded the Esalen Institute in Big Sur and is considered a leader in the human potential movement.

As he embarked on his first book, Murphy didn’t expect “Golf in the Kingdom” to resonate the way it did. Lynn Marriott, a well-known Swedish golf coach, interviewed for a teaching/club instructor position on Cape Cod – and found the book to be required reading for all applicants.

Murphy didn’t try to explain how to play golf in his book. It’s taken a winding and entertaining path in trying to illustrate the “peculiar genius” of the game and why so many people find it fascinating.

“It got me thinking in different ways,” said Bay Area golf instructor and former PGA Tour pro John Abendroth. “I played several games at night, solo, and really enjoyed them.”

In some ways, Murphy’s book foreshadowed modern sports chatter about climbing in “the zone.” An example: Stephen Curry throwing a 3-point shot and turning to run down before the ball rips the net. He knows he succeeded.

Former Tour pro Bobby Clampett had a similar experience when he twice landed shots from the fairway at Champions Tour events. On the first, television cameras caught Clampett declaring “Exactly the shot I was trying to hit” and “Come in!” as the ball flew to the green. He landed in the hole on the fly.

On the second shot, 191 yards out, he said he knew the shot was “absolutely perfect” as soon as it left the clubface. The ball again disappeared into the hole on the fly, this time to complete a back-nine 29.

“It was a supernatural experience, clearly,” Clampett said.

All these years later, Murphy still relishes the challenge of articulating the mystical appeal of golf. He started with location and what he described as the “expanded boundaries” of a golf course, in stark contrast to the confined playing field of other sports.

Then there’s the time element: golfers typically spend four or five hours navigating a course, with no rush.

“You play in the biggest garden collections in the world,” Murphy said. “Some of them are so gorgeous, like Pebble Beach. … (Acclaimed Creator) Alister MacKenzie had radar for the prettiest rooms.

“You have to slow down, you play and you look around. Part of it is just being exposed and immersed in stillness, and it puts you in a sort of contemplative mood.

Murphy chuckled sheepishly as he shared examples of the book’s lasting impact. He befriended Hall of Fame basketball player (and former U.S. Senator) Bill Bradley during his New York Knicks days; Both Bradley and Phil Jackson read “Golf in the Kingdom” when they were teammates.

Jackson, known for his zen-like ways and meditation as a coach, then gave the book to Michael Jordan, according to Murphy. Still, he knows that many athletes and coaches (including Brodie) have been reluctant to speak about it publicly over the years.

Murphy referenced criticism of what he half-jokingly called “woo-woo metaphysics”. The thrill of seeing a golf ball fly over the countryside may have “a mystical quality,” as he writes in the book, but it feels squishy to many non-golfers.

“There are a lot of tough-minded people in the sports world who say we’re here to master the sport and win the game, but not to talk about those mystical experiences,” Murphy said. “Any new element that emerges in a culture must be tested by the culture. …

“A part becomes moral. You’d think we were having secret love affairs on the seventh hole. Why would people be so offended by this? It’s not common, but it has taken on a moral dimension.

The book was not an immediate success. It only sold about 5,000 copies in its first two years, according to Murphy’s recollection, despite receiving a positive review in The New York Times and another favorable review in John Updike’s New Yorker magazine.

Soon after, as the book gained traction, sales topped 10,000 a year, then soared to over 50,000 and later to over 100,000 a year. It has become a celebrity favorite, both in sports (particularly on the golf tours) and in the world at large. Bill Murray touted him on morning talk shows, accelerating his rise in another realm.

“I’ve never missed a royalty payment in 50 years,” Murphy said, a hint of astonishment in his voice.

Even now, half a century after the book was originally published in the spring of 1972 (it was republished this year), he is surprised by the reaction. Whenever he golfs or makes an appearance on a course, someone “almost always comes to tell me about their latest mystical or occult experience,” Murphy said.

He wrote at least 10 other books, from “The Psychic Side of Sports” (1978) to “The Future of the Body: Exploration into the Further Evolution of Human Nature” (1992), but none were as popular as ” Golf in the Kingdom.”

“It was a blessing to write this book, but it points to an eternal truth,” Murphy said. “People love sports because it has many secret magics, and golf is perhaps the most enchanted of them all.”

Ron Kroichick covers golf for The San Francisco Chronicle. Email: [email protected] Twitter: @ronkroichick