The release of “A Wrinkle in Time” — the eagerly awaited adaptation of Madeleine L’Engle’s 1962 Newbury Medal-winning children’s fantasy novel — has got me thinking: Is there a secret to turning a beloved book into a beloved movie?

It’s not the first time the question has crossed my mind over a 22-year career reviewing movies that has caused me to ponder why the “Lord of the Rings” trilogy was such a satisfying moviegoing experience and the adaptation of Stephen King’s “The Dark Tower” was so terrible. While talking to filmmakers, as well as to authors whose works have made that fraught transition from page to screen, I have posed the question many times. Again and again, the answer has come back. It evokes an open marriage: Be emotionally faithful to the source material — but don’t be afraid to stray.

Ritesh Batra put it best. When I interviewed the director of “The Sense of an Ending,” the 2017 film based on Julian Barnes’s Man Booker Prize-winning novel, the filmmaker told me that the best — and most liberating — advice he ever got was what Barnes told him: “Go ahead and betray me.”

The real question for anyone adapting a book, Batra explained, is not to ask, “What do I want people to see on-screen?” — i.e., plot, action, etc. That’s the easy part. Rather, it’s “What do I want people to feel?”

I proposed the theory — that feeling trumps seeing — to Jennifer Lee, whose “Wrinkle” screenplay (co-written with Jeff Stockwell) forms the basis of director Ava DuVernay’s new film. “It’s funny,” Lee said. “That’s exactly what I say about the approach we took.” Lee’s previous credits include co-directing and writing the Oscar-winning movie “Frozen,” based on a story by Hans Christian Andersen.

The challenge of book adaptation, Lee explained over the phone — particularly when the book’s audience is children, who carry attachments to favorite books for years — is that readers fill in missing details with their imaginations and that a movie “chooses for you.” An additional problem is the fact that film is collaborative: a product not just of words on a page, but also of makeup artists, costumers, casting agents, production designers and, if you’re lucky, a director with the vision to unify it all. There is only so much that a writer can nail down.

Referring to Reese Witherspoon’s shape-shifting Mrs. Whatsit, one of three guardian-angel-like beings who guide “Wrinkle in Time’s” child protagonist, Meg Murry (Storm Reid), through interplanetary adventures in search of her missing father (Chris Pine), Lee acknowledged those limitations. “I couldn’t say, ‘This is Creature Whatsit. This is what she looks like.’ I’d have to say, ‘This is how I felt when I saw Creature Whatsit.’ Ava has got her own beautiful interpretation of Creature Whatsit. The only thing I could bring to that is, ‘What does this moment feel like?’ ”

The new movie’s depiction of that critter, previously rendered as an awkward, Pegasus-like hybrid with an oversize human head in Disney’s first attempt to adapt the novel — a poorly received 2004 TV movie — is not the only place where, Lee said, the film invokes artistic license. Certain minor characters in the book have been pruned and combined into a single character. And Mrs. Who (Mindy Kaling) — so notable in the book for her propensity to pepper her conversation with archaic foreign maxims — drops some surprisingly contemporary quotes.

“We loved the concept of a character who has evolved past language, and who therefore uses other people’s words,” Lee said. “That was so fun. We said, ‘Well then, she should have access to the entire canon of everything that’s ever been said.’ She could go to Shakespeare, she could go to Buddha if she wants. But she also can go to Jay-Z.”

As for the book’s villain — a malevolent alien entity called IT that seeks to convert mankind into conformist automatons — Lee said she was adamant about avoiding L’Engle’s description of a giant, disembodied cerebellum on a slab. “I made the decision early on that the characters should not be standing there looking at a pulsing brain,” she says.

One of the most significant changes, according to Lee, is in the casting of Zach Galifianakis as the Happy Medium, a seer who, in L’Engle’s telling, is not just a minor character, but a she. According to Lee, turning the Happy Medium into a dude — one who helps Meg to dig deeper into what Lee calls Meg’s “wounds about her father” — is the key that unlocks the whole story.

Lee described the character of Mr. Murry (Pine) — at least as written in the book, which has sometimes been criticized for its underdeveloped characters, among other things — a “MacGuffin.” Popularized by Alfred Hitchcock in the 1930s, the term refers to a narrative device that serves to advance the plot, but little else. In Lee’s screenplay, Pine’s character gets fleshed out, allowing viewers to better understand both what Meg loves about him and where her fears of abandonment come from. The Happy Medium — a character whose very name plays on the notion of balance — becomes a kind of father figure in the movie, says Lee, shedding light on aspects of Meg’s difficult relationship with her father that are only superficially explored by L’Engle, if at all.

Speaking of balance, Lee’s favorite movie adaptation of all time is Ang Lee’s “Sense and Sensibility,” a movie whose screenplay — written by the movie’s star, Emma Thompson — is the “perfect” synthesis of the two competing demands of adaptation: fidelity to both literary nuance — embodied in Jane Austen’s 1811 novel — and the literalness of cinema. Too much faithfulness, she cautioned, is overrated.

“You should never try to be the other thing,” Lee said. “You should never try to be the novel. You’ll fail.” The trick of adaptation lies not in going where a book goes, but in getting to where the audience needs to be. “Wrinkle,” Lee explained, may take Meg — and us — on a journey from planet to planet, one that jumps, by folding the fabric of time, from Earth to Uriel to Camazotz to Ixchel, and then back again. But the real journey, she said, is an emotional one.

That road map, Lee said, guided every decision she made about what to keep, what to invent and what, if necessary, to cut from the book for the movie, if it distracted from the trip. The question, Lee said, is not “How can I tell this story?” but “What is it going to take to feel this story in the way we need to feel it?”