When Jennifer Venditti was a child growing up in Saint Paul, Minn., in the days before cellphones, her parents would sometimes deposit her with a babysitter for the night, leaving a contact number for where they’d be.

Ms. Venditti, not yet 10 years old but restless and curious, would pick up the house phone and call, pestering her mother about the details of the night: what the house looked like, what people were wearing, what everyone was talking about.

“I didn’t watch TV,” Ms. Venditti said last month, in the SoHo office of her casting agency JV8 Inc. “I wanted to go out into the world. I wanted to go to the mall. I wanted to go to the train station. I wanted to go to the airport. I wanted to watch people living.”

From then until now, she has been afflicted with a voracious appetite for humanity in all its mundane glory and glorious mundanity. That hunger has helped Ms. Venditti become an acclaimed casting director, and a signature one, too, particularly for films and television shows in which the genuine and the fantastical seep wordlessly into each other: “Uncut Gems,” a drama of crime and infidelity in and around New York’s diamond district; “American Honey,” about the chaotic relationships within a roving pack of teenage magazine sellers in the Midwest; “Euphoria,” about disaffected and dissolute teens in the suburbs.

You can tell a Venditti production — which typically blends nonprofessional actors with professionals — from the creases, the unexpected patina, the uncanny gestures that seem to unfold at a slightly different speed than most fictional work. From a distance, it can appear to be an aesthetic choice, but in actuality, it’s a philosophy that manifests visually. Often it feels as if the pros are softening to match the naturalism of the rookies, more than the other way around.

This week, Ms. Venditti will release her first book, “Can I Ask You a Question?: The Art and Alchemy of Casting,” through the film production company A24 (“Moonlight,” “Zola,” “Minari”). It’s a monograph about her process, but really a visual diary of how to see people: casting photos teeming with asymmetrical faces, assorted body postures, bold sartorial choices made far from fashion runways. In the eyes of some, these are bit players, background accents. For Ms. Venditti, each is a potential universe.

“The JV8 lens,” said Michele Mansoor, one of a handful of freelance scouts Ms. Venditti has employed for years, “is to see the cinema of actual life.”

Though the walls of Ms. Venditti’s office are covered in Polaroids of models and personalities and local eccentrics, she averred, “I say this with respect, but I don’t identify with the casting director title.”

Ms. Venditti, 50, got her early breaks working in fashion, securing real-people models in unlikely locales for W magazine — say, for a shoot in West Virginia of Robert Frank-like photos. “For finding people, there wasn’t anyone who could even come close to Jen,” said Dennis Freedman, who was W’s creative director, “And also for her empathy and her true caring about the people that she cast.”

In the era of flush fashion magazine features, her work, alongside both fashion and art-world photographers, blurred falsity and reality, constructed glamour and naturalistic confidence. She also worked on Rodarte runway shows, casting models through long conversations. “Jen will ask questions that could feel invasive from someone else,” said Laura Mulleavy, who designs Rodarte with her sister Kate. “She can talk to someone, and they will tell her their life story.”

Ms. Venditti began to transition into casting work for film in the mid-2000s, and on one of those assignments, in Maine, she happened upon Billy Price, a shy, earnest and awkwardly confident high school student who captured her attention. “Billy the Kid,” the poignant documentary she directed about him, was released in 2007.

Mr. Price became a foundational Venditti character: a young man creating his own reality, living it loudly amid everyone else’s store-brand truth.

Mr. Price still lives not far from where he grew up — when he answered his landline, he spoke with the same deliberate curiosity as in the film. Before Ms. Venditti put him on camera, he said, “nobody really found me fascinating. A lot of people found me to be the guy to make fun of or something.” Throughout the process, he said, Ms. Venditti “was there for me, just like my mother was. If I wasn’t comfortable doing something, she would say, ‘OK, we won’t do that then.’”

“Billy the Kid” became a calling card for directors looking to imbue their fictional projects with deep vérité. Ryan Gosling sought her out for his directorial debut, “Lost River.” “I wanted my film to be populated with people that had the same richness of character I had experienced in my life,” he said in an email. “I knew that working with her was the only way I was going to be able to achieve this.”

When she screened the film at the South by Southwest film festival, she met Josh Safdie, sparking a relationship that would lead to her casting the movies “Good Time” and “Uncut Gems,” which he directed with his brother Benny.

“She does these epic hourlong interviews, which are basically talking heads of people’s lives, and you really get to know somebody,” Josh Safdie said. “Those are more valuable than the auditions.”

In conversation, Ms. Venditti, who is tall but not imposing, leans in to display attentiveness and empathy, and rarely interrupts, preferring instead to let her interlocutor dictate flow and pace.

“She knows how to handle people,” said Wayne Diamond, lion-maned garmento turned “Uncut Gems” scene-stealer, calling in from Soho House in Miami. “I mean, I do this as a hobby. When I go out for these auditions, some of these casting directors, you want to just, like, shoot ’em, you know?”

For “American Honey,” directed by Andrea Arnold, Ms. Venditti spent long stretches of time scouting in Panama City Beach, Florida. The time out in the field, and the footage and experience gathered, became a de facto part of the film. “What it did is it informed all the other departments,” she said. “It created an environment on set that almost made it feel like a documentary.”

Riley Keough, one of the film’s stars, sent in several self-taped audition videos before eventually being called in by Ms. Venditti, whose audition process was new to her: casual conversation, personal questions, hand-held camera, movement.

“It feels like you’re shooting a scene,” said Ms. Keough, calling in from a set in New Orleans, before pausing to receive a Covid test swabbing, then adding, “It feels like the way auditioning should be.”

Ms. Venditti takes that same unconventional process regardless of the aspirant’s experience level. Angus Cloud, now Fezco on “Euphoria,” was discovered on the street by one of her scouts. Ms. Venditti loosened him up on camera with questions about his life and taught him to improv. “She kind of, like, just gives off that family, that aunt vibe, you know? That motherly vibe,” Mr. Cloud said in his now-signature wheezy purr, calling in from the back porch of his Los Angeles home. “I got a lot of love for her.”

Ms. Venditti utilizes a network of trusted scouts, but finding raw talent in the wild is an ever more elusive game. Thanks to social media, everyday people are thrust into the role of performers, putting themselves forward at all times, hoping to bait the algorithms and, in turn, your eyes.

“The person that wants to be found, in my experience, is never who I want to find,” Ms. Venditti said.

That brings its own set of challenges. “There’s a social work aspect,” Ms. Mansoor said. “One of the most important things I learned from Jen is to not only manage my expectations, but not to sell a dream. It’s a big responsibility to walk around as the bridge between people’s everyday lives and these really crazy, once-in-a-lifetime opportunities.”

In the book, Ms. Venditti relates a tale about returning to West Virginia to discover that a model she had spent time with, and prominently featured in W magazine, had fallen on hard times. She promised to try and help her.

“When I first started, I didn’t understand the boundaries,” Ms. Venditti said. Now, she tries to locate value, for herself and her subject, in the experience itself. “I do think there’s a healing in somehow being seen,” she said. “I think hearing someone’s story, reflecting someone’s story, does create an alchemy in a way, and that is what I’m interested in.”

(Currently, she is casting “The Sympathizer,” an HBO series directed by Park Chan-wook based on the novel by Viet Thanh Nguyen, which won a Pulitzer Prize in 2016.)

She maintains close ties with many of the people she has cast over the years. “I do wish I knew more about her home life,” Mr. Price said. “I do know she’s got a dog. Last time we spoke, you know, she had to let me go because she found a tick on her dog. I hope the dog’s OK.”

Mr. Cloud, who shares a birthday with Ms. Venditti, sends friends her way for potential opportunities, and she put his sister up for a role on “Euphoria” (which she did not get). “I wouldn’t put nobody in touch with someone I didn’t trust,” he said.

Ms. Venditti is also producing the first film Ms. Mansoor is directing, a documentary about a group of young people Ms. Mansoor encountered in Columbus, Ohio, while scouting for a different project, a parallel to how Ms. Venditti found Mr. Price.

But apart from some time working on a project about the town in Sicily where a woman hoped to create a never-ending film festival with the inventory from Mondo Kim’s, the storied New York institution, Ms. Venditti hasn’t returned to directing.

Josh Safdie, though, emphasized the power Ms. Venditti exhibits in her métier: “I believe when she does all these audition tapes, they are a form of filmmaking.”

When Ms. Venditti’s father fell ill with leukemia in 2015, she moved him into her Carroll Gardens apartment in Brooklyn to take care of him. As he got sicker, she noticed that his personality, which she had often bristled at, was shifting. Some essential performance he had been enacting for his whole life was melting away.

It made her think differently about what she was seeking in other people. After her father died in 2016, she studied to become a hospice volunteer. “The hospice training was learning to just be a container,” she said. “You’re doing it wrong if you try to help someone or fix someone.”

Receiving, not seeking, became her goal. Now, even though there are umpteen casting videos and TikToks and Instagrams and YouTubes to look through, she still finds herself in search of something that’s perhaps too primal to be caught on tape.

Last year, Ms. Venditti was diagnosed with Lyme disease and began receiving treatments in an IV clinic, in a room alongside several other people.

“I compare it a little bit to jury duty, but it’s a more vulnerable state,” she said of the grab-bag of personalities in the room at any one time. She laughed a little at her old self: “Before, I would be trying to cast those people.”

Instead, she simply tries to be present. “It’s death. It’s mortality. You’re just in this room, having the human experience,” she said. “It gives me goose bumps.”