In my mental catalog of Judy Blume books, everything is filed according to the adolescent trope it taught me about. It’s Not the End of the World is the divorce book. Forever… is the sex book. Then Again, Maybe I Won’t is the wet dreams book, which in the fifth grade read like an intelligence report sent from behind enemy lines. Are You There God? It’s Me, Margaret, first published in 1970, is, of course, the period book.

Or at least that’s how I remembered it from being 10 years old: Margaret and her friends competing to see who will get their periods first; that awful Nancy lying about getting it and then crying in the bathroom of a fancy restaurant when it actually came; Margaret alone in her room, fumbling with the mysterious belt that sanitary napkins used to have in the ’70s. Girls read Are You There God as a supplement to middle school health classes, was what I vaguely concluded, so they would know what it felt like when their periods came. (I could not imagine a boy reading this book for any reason whatsoever.)

So I was startled, when I watched Kelly Fremon Craig’s excellent new film adaptation of Are You There God, to see that there were so many other plotlines at work in the story. There was all this stuff about bras, which I did vaguely recall. But then there were also friendship dynamics and family dynamics and new town stuff and religion stuff — my god! How had I forgotten the religion stuff? It’s right there in the title!

It didn’t make sense to me. The damn book is only about 30,000 words long. Could Blume possibly have fit that much in there besides the period plotline? Had Craig added something new?

Not really, I discovered upon returning to the book for the first time in 25 years. Nearly everything in Craig’s film is in Blume’s book, too. As it turns out, Are You There God? It’s Me, Margaret is a lot more than just the period book. It hits all the tweenage low points, and it welcomes adult readers with a surprising amount of grace.

Are You There God begins with Margaret Simon, 11 years old, moving out of New York’s Upper West Side and into the suburbs of New Jersey. In a gently understated subversion of the city kid stereotype, she finds when she arrives that she seems younger for her age than the jaded suburbanites all around her. Queen Bee Nancy, who immediately takes Margaret under her wing, already plays with makeup and practices kissing boys, while Margaret does neither. Nancy seems, Margaret notes, impressed and resentful, “to know a lot.”

Toxic girl friendships are one of the great themes of Blume’s oeuvre (explored in their darkest form in the harrowing Blubber). Accordingly, once Nancy enters the picture, Are You There God becomes the story of Margaret’s education and corruption. Nancy pushes Margaret to buy a training bra and sanitary napkins, teaches her to perform her crushes, tells her which boys are acceptable crush objects. She plies Margaret with cruel gossip to turn her against the girl in their class who already wears bras.

It’s Nancy who informs Margaret that her secular existence is a problem. The Simons identify as neither Jewish nor Christian after Margaret’s mother, Barbara, was disowned by her Christian parents for marrying a Jewish man. In New York this wasn’t an issue, but in the suburbs, Nancy tells Margaret, everyone joins either the Y or the Jewish Community Center.

Desperate to follow Nancy’s instructions, Margaret embarks on a research project to try to find what religion is best for her. She isn’t looking to be shown how to talk to God: She already does that every night, alone in her room, pouring out her dreams and worries to God as though she’s writing in her diary. (“Please help me grow God. You know where.”) Instead, Margaret wants organized religion to codify her relationship with God, to turn it into something that Nancy will be able to categorize neatly away in the same way she does everything else.

Picking a religion wouldn’t only help Margaret with her school friends. It would also help her with her family. Simmering mostly below the surface of Margaret’s naive narration is a proxy war between her parents and her grandparents, with Margaret’s life as the battlefield.

Margaret is devoted to her paternal grandmother, Sylvia, who dotes on her, paying for her New York City private school tuition and her New Hampshire summer camp. Sylvia feels fiercely that Margaret should grow up as a New York Jew, in culture if not in religious belief, and to that end shows up uninvited at the Simons’ new house with bags of deli food to make sure Margaret will remember what it should taste like. “Mmm … nothing like the real thing!” she says every time she bites into a pickle.

Margaret is vaguely aware that her mother doesn’t particularly like for Sylvia to be so involved in Margaret’s life, and she’s pretty sure that they moved to New Jersey specifically to get Margaret away from Sylvia. She’s less aware of how many times Sylvia tells her to do something and then follows it up by instructing her not to tell her parents. It all explodes, though, when Barbara’s parents show up in town to check up on their granddaughter, forcing Margaret to miss a planned visit to Sylvia.

“Margaret is a Christian!” says Barbara’s mother.

“You’re a Jewish girl,” Sylvia assures Margaret.

“I’m nothing, and you know it!” proclaims Margaret. “I don’t even believe in God!” (To us she adds, “I wanted to ask him did he hear that!” She is, at the time, in a fight with God.)

It’s this plotline that Craig gently expands, mostly through transforming Barbara (played here by Rachel McAdams at her warmest) into a point-of-view character. Craig’s take, though, is less an addition to Blume’s text than an excavation, working with what Margaret tells us to unearth new details in the story.

Blume’s Barbara is an artist who seems a little scattered in the suburbs and lightly on edge around her mother-in-law. Craig’s Barbara, in turn, is a bohemian who moves to the suburbs because she thinks it will be best for her child and then finds herself losing her own identity; who would like her mother-in-law to stop trying to raise her daughter for her now, please. In the film, Barbara becomes a stand-in of sorts for all the women who grew up on Judy Blume and are watching Craig’s film now as adults. Through Barbara’s eyes, we watch Margaret care passionately about things like not wearing socks with loafers and buying a bra well before she needs one, and we remember what it was like to care so passionately.

All of it is consistent with the characterization Blume gave us, back when she wrote Margaret as a newly suburban housewife herself, writing books in between caring for her children. It’s just the stuff that Margaret, with the complacent solipsism of childhood, never bothers to lay out for us. She’s too busy trying to figure out how to be the version of herself Nancy and her parents and her grandparents want her to be — until she figures out how to be a version of herself that she likes instead.

Once she figures it out, you know what happens next: She gets her period.