Beautifully acted and suffused with warmth and humor, “Are You There God? It’s Me Margaret” is a film worthy of thelong wait in bringing Judy Blume’s classic 1970 children’s book to the screen.

Director-screenwriter Kelly Fremon Craig, who made 2016’s equally accomplished “The Edge of Seventeen” about a slightly older girl, here captures the uncertainties and thrills of 11-going-on-12 Margaret’s (Abby Ryder Fortson) move from New York City to the New Jersey suburbs as she also navigates puberty.

The endearing, quietly expressive Ryder Fortson is fully up to the task of being an avatar for generations of readers who saw themselves in Blume’s beloved protagonist. She leads a uniformly winning young cast that includes Elle Graham as Nancy, energetic ringleader of a secret society whose members, including Margaret, must wear bras even if they do not need them; Amari Price and Katherine Kupferer as fun-loving fellow Nancy acolytes; and Aidan Wojtak-Hissong as Margaret’s slightly older crush.

Tim Ives’ buttery cinematography and period-perfect cars, clothes and furniture place us distinctly in the early 1970s. But Fremon Craig wisely keeps the story’s scale myopically Margaret-sized, unencumbered by mentions of the Vietnam War or the economy.

Within this preteen world, the stakes of a move to the suburbs could not be higher, since it means leaving Margaret’s beloved grandmother, Sylvia (Kathy Bates). When Margaret returns from camp to New York to find parents Barbara and Herb (Rachel McAdamsandBenny Safdie) packing moving boxes, she directs her concerns to God, kicking off an ongoing private conversation with the deity she has “heard great things” about. She would not know firsthand because her Jewish father and Christian mother have left it up to her to choose a religion, as an adult.

Margaret inquires with God about religion, but also requests she mature faster, because developing breasts and starting one’s period apparently arethething to do in the Garden State. Nancy, who barges her way into Margaret’s new house and life, is obsessed with her own and others’ development, and charismatic enough for the other girls to become equally obsessed.

Blume’s frank discussion of puberty was revolutionary when the book came out. All these years later, the film’s centering of it still feels like a revelation — perhaps because reading the book was as private an experience as Margaret talking to God, and movie-going is a shared one. Regardless, filmgoers of all ages will benefit from the movie’s direct yet often lighthearted approach to this topic.

Ryder Fortson and Price lean into the humor when their characters hit the local drug store to buy sanitary pads to “practice” with, only to encounter the worst possible scenario at checkout.

McAdams is as great as a nice mom as she was amean girl in the 2004 Tina Fey comedy. Through Barbara’s and Sylvia’s storylines, Fremon Craig tucks subtle commentary on women’s limited opportunities at the time into Margaret’s story. As Margaret adjusts to her new school, Barbara tries to acclimate to staying home all day instead of hustling up art-teaching gigs, as she did in New York.

Always exuding affection for Herb and Margaret, but too conscious of their absence when they leave for the day, Barbara volunteers for every committee at Margaret’s school, dutifully follows pot roast recipes and tries to make a real go of being a homemaker. But the deft McAdams offsets Barbara’s seemingly sincere enthusiasm with an anxiousness her character can’t shake.

If the “stay-at-home” part challenges her, the “mother” part brings Barbara obvious joy. Ryder Fortson and McAdams share a believable familial chemistry built on their characters’ mutual respect.

McAdams and Safdie bring a lived-in ease to their characters’ relationship that, as the movie will reveal, took work to achieve. Safdie, co-director of the dark, frenetic indie films “Good Time” and “Uncut Gems,” is improbably perfect as a laidback suburban dad.

Barbara’s and her mother-in-law’s less loving if cordial interactions seem authentic to their time. With women’s roles so rigidly defined, Sylvia cannot help but view Barbara, who has more daily access to both women’s favorite people, Herb and Margaret, with some envy.

But Sylvia is a bright presence, with grandmother’s and granddaughter’s mutual adoration evident every time Fortson Ryder and Bates share the screen. A shot of the pair’s spontaneous hug after they catch a Broadway show captures the special magic that results from being fully entertained in a big city with a loved one at your side.

Carla Meyer is a freelance writer.