In Book Club, Diane Keaton plays a woman clad in immaculate suits who charms everyone with her warm, scattered demeanor. Also, her name is Diane. And she’s wearing clothes that literally came from Keaton’s closet. Of all the “Diane Keaton” roles the Oscar winner has played before, it’s Book Club that contains the most meta performance of all—which was intentional.

“In the original draft of the script, Diane was our archetype for the character,” director and co-writer Bill Holderman explained in a recent interview. The first-time director and his co-writer, Erin Simms, first dreamt up the idea for their film—a romantic comedy about four best friends (played by Keaton, Jane Fonda, Candice Bergen, and Mary Steenburgen) who bond over reading the Fifty Shades of Grey trilogy—back in 2012. That year, Holderman sent his mother the Fifty Shades books as a cheeky Mother’s Day gift. Simms, who initially thought that idea was absurd, quickly followed suit. That inspired them to write the film, with the role of “Diane” strictly envisioned for Keaton. (Fonda’s role was also written specifically for her, though her character’s name was later changed to Vivian). Keaton is among a select group of actors who can often be found playing a dramatized version of herself on-screen—which is sublime when it works, and incredibly frustrating when it doesn’t.

Holderman and Simms didn’t know if Book Club would pass the Keaton Test. But then came the “surreal” part, Holderman said: Keaton’s agent was interested in the script, and sent it on over to her. Soon, Holderman was summoned for a meeting with Keaton herself.

Pause, for a moment, here—what do you imagine a meeting with Diane Keaton is like? Full of light and laughter? Perhaps, in your imagination, she walks in carrying an ice-filled glass of wine in one hand, an iPad open to her highly curated Pinterest page in the other? You imagine levity, whimsy! But no: that’s just Keaton’s on-screen persona. In real life, she’s a lot more scrupulous.

“I think the first thing she said to me, before she even said ‘hello,’ [was]: ‘I can’t be in a bad movie. This can’t be a bad movie,’” Holderman recalled. “So that’s sort of how Diane Keaton enters a room.”

The actress was wary, at first, of Holderman’s lack of directing expertise; his film experience is mainly in producing Robert Redford dramas like The Company You Keep and The Conspirator. And Simms was a first-time screenwriter.

“She said to us, ‘Well, what makes you think you guys are gonna make a good movie?’” Simms said of their next meeting with Keaton. “‘I’ve heard this before from first-time directors.’”

Keaton—who, Simms noted, walked in wearing “the most badass three-piece suit”—was charmed by the character on the page, however: “One of the other first things she said was, ‘Well, I know why you guys came to me.’”

Keaton was the first star to officially board the project. She also recommended Andy Garcia—they’ve been friends since co-starring together in The Godfather: Part III—to play Mitchell, her character’s suave love interest. The cast was later rounded out with Don Johnson (father of Fifty Shades franchise star Dakota Johnson), Richard Dreyfuss, and Craig T. Nelson. The four core actresses had never acted together in the same film—a thrilling prospect. They were also excited to play fully realized roles that didn’t sideline them as one-dimensional, ladies-of-a-certain-age supporting characters. The women in this film are bursting with personality, each one chasing an adventurous, sexy pursuit inspired by the naughty adventures of Anastasia Steele. (Early on, the script got the blessing of Fifty Shades author E.L. James.) But offscreen, not all the actresses were terribly familiar with the book series.

“Jane Fonda had read it,” Holderman said. “Mary Steenburgen is quick to tell you she leafed through it for the naughty bits. Candice Bergen claims that she started it and someone stole her copy.”

”Her housekeeper,” Simms added. “Diane—she read it, but she’ll never admit it!”

Keaton has maintained that she’s never read the book or seen the movies—though there is proof that she’s read at least a snippet of it. In the film, her character reads part of the book aloud, laughing her way through some of its saucier descriptions. It’s a scene that’s pure Keaton—reacting to the book’s contents, giggling at James’s X-rated prose. But of course, every frame of the performance is pure Keaton, considering how closely the actress mirrors the character she plays. Her performance was also aided by real items from Keaton’s wardrobe. Take, for example, the gray poncho she puts on in the trailer as she prepares for her first date with Mitchell. That was actually an item Keaton brought in after the costume team realized the original look they had prepared wouldn’t pair well with the scene.

“The jacket that we had for her was too elegant, and it wasn’t gonna work for the comedy,” Holderman said. “Diane herself was like, ‘You know what? Don’t worry, I live 10 minutes from here.’ And she got in her car, drove home, grabbed a bunch of incredible designer pieces and brought them back, and that was one of them.”

Such is the magic of casting Diane Keaton to play Diane Keaton.