In a way, it's kind of a funny thing that Judy Blume at 43 is just beginning to communicate with her own mother.

In another way, of course, it is part of what has made Judy Blume the Judy Blume, this sense of her own loss, this urgent feeling that there simply must be communication. It is a theme that recurs again and again in her books and, she firmly believes, one that has played a role in getting her books swept from school library shelves across the country -- "Blubber," for example, is unavailable in Montgomery County schools without teacher guidance, and "Forever," because of its explicit sex scenes, is unavailable, period.

And it's part of what's gotten her on to the Moral Majority hit list.

Communicating -- exploring the feelings of childhood and adolescence is part of it -- also explains much of her popularity. She tells a good story as well, of course, and she says she cannot begin to guess how many copies of her 14 books have been sold worldwide. Once they passed the 8-million mark three or four years ago, she lost track. "We were trying to figure it out the other night," she says. "It's got to be millions and millions and millions . . . maybe 50."

Communicating between parent and child, she says, "is a major problem today. My mother is still tuned into 'Are you happy?' That's always the first question . . . and I've tried desperately to make my mother think that everything was fine in my life. I could never admit to the pain or disappointment I might have been feeling, right up until the time I was 35," when her first marriage broke up.

Judy Blume's father, who was a dentist, died when she was 21. "And," she says, referring to her mother, "we never talked about it."

She believes she is beginning to understand. She has a theory. "I think a lot of the censorship is based on fear, this fear that if 'my child reads one of your books, Judy, my child is going to come to me with questions and I don't want to deal with those questions' . . . It gives certain parents a way out. You can hook up with the side that's trying to ban the books, and use it as an excuse for not facing up to communicating with your kids."

She has actually had parents tell her, for example, "I learned about sex on the street and that's good enough for my kid."

Judy Blume is a slight and pretty woman, 43, but younger looking. Her brown eyes are bright and warm and intense. She uses her hands a lot when she speaks, but winces occasionally when she is painfully reminded of the backache (her first ever) she woke up with. The pain comes especially when she laughs, which she, nevertheless, does quite often.

She also winces when she is asked if she's had a nose job, but it doesn't seem to be because of her back.

"That's a heavy question," she says. And smiles. She has written about a nose clinic with compelling verisimilitude in her "adult" book, "Wifey." "Yes," she says, she's had "a sort of half-job." But it wasn't until she was 35 and because her nose had been broken twice. "Partly out of vanity," she concedes.

(She says she thinks her nose is quite crooked. It doesn't look crooked at all. She is sounding like one of her characters.) "And I really can breathe better," she adds.

She is in the process of moving back East from New Mexico where she's been living for the last five years or so. Her New York apartment, into which she was to have moved in mid-August, is still not finished. She does her work in one library or another, and she has been settling her two children in their respective colleges, visiting her brother (an EPA official here) and recasting her newest book, "Tiger Eyes," into a TV script.

She has been married twice and is now "living with." "He's a very private person; nobody famous."

She has tried very hard to "be there" for her own two children and believes that she has succeeded. "I used to talk about them a lot more," she says, "but now they're older daughter Randy is 20; son Larry, two years younger and they want their privacy, too. It was," she says carefully, "a big thing in my life to be able to say that my children are these individual human beings, and I've got to get rid of the expectations that seem to come almost automatically."

Brought up on Nancy Drew, all the Oz books and a few others, and especially influenced by Maureen Daly's "Seventeenth Summer," Judy Blume has included in her books such things as nose-picking, breaking wind, throwing up, grandmothers who have sex lives, sex-crazed 12-year-olds who wish they did and say so and 15-year-olds who fall in love and make out.

Her books are a scatalogical and soft-porn cine'ma verite' of childhood, of puberty, of growing up. Menstruation, wet dreams, masturbation, all the things that are whispered about in real school halls are written about here.

Some of her fourth- and fifth-grade characters use the "f" word in more four-letter glory than is permitted here (and not as an expletive), but they all have real feelings, real anxieties and, and this is very important to her, real humor.

"You wonder where does all the humor go," she says, "when people grow up. I have a theory that parents are afraid that if they laugh with their kids, they're giving up some kind of authority.

"I think it's really healthy to laugh with your kids, whatever it is -- their bathroom humor, their nonsense humor . . ."

Blume writes for ages 4-or-so to 40-or-so. But it is the books aimed at early teens (which are mainly devoured by the 7-to-10 set) that seem to have the biggest success with children -- and the biggest problem with their parents.

A good example is "Blubber," which is about being left out, picked on by one's peers and generally victimized by the vicious little animals almost all kids that age (11-ish) are.

It is a no-holds-barred inside look at the cruelty of childhood. Kids eat it up. It continues as one of the all-time top Blume best sellers. Adults complain that it lacks "moral tone," says Blume, that such actions cannot go "unpunished."

The book deals so explicitly and so painfully with the agonized feelings of both victimized and victimizers that, says Blume, "I cannot understand it when a parent says, 'You didn't tell them this was wrong' . . . The most intelligent and most wonderful letters to the editor of The Washington Post during the controversy over "Blubber" in Montgomery County in 1980 all came from the children, and the parents sounded like we expect children to sound like. But, of course, kids are often much more able to deal with things."

She was in a debate recently with a representative of the Moral Majority whose main complaint about Judy Blume books was that "they teach values."

She says, "What he means, of course, is you don't want to give children the idea that they can think, that they can make value judgments and they can question our authority, and so the best thing to do is prevent them from reading these books.

"Well, maybe you can control a lot of other things, but you can't control your child's mind."

Judy Blume started writing during her mid-twenties when she was stuck at home with her two small children. She felt creatively starved, she recalls, and started out to better the picture books her youngsters were into as toddlers.

She found herself writing about 12-year-olds because she had felt that time of her own life to have been more exciting, more rewarding, more full of adventure than the life she led as housewife-mother.

What about the criticism that her books aren't good literature, that her heroines are little more than anatomically correct Nancy Drews?

"What is literature?" she counters. "I don't care what they say as long as the kids are reading it, and as long as they're identifying, or in some way emotionally involved. If they're touched by something, care about something, who cares what those who have to label it say? I don't care."

Pause. Another smile. "Well, I do care. I care, but that's not what's most important. Because kids aren't into labels, right? That all comes from the adult world. I don't get as angry about any of it as I used to. I'm 'mellowing out,' as my kids say."

Blume has declined lots of opportunities to capitalize on her popularity -- Judy Blume bras, Judy Blume jeans, Judy Blume T-shirts. "How," she asks in mock wonderment, "about a board game called 'Growing Up With Judy Blume?' Your parents get divorced, move back eight spaces; get your period, you move ahead six spaces . . . People," she sighs, "will cash in on anything."

She is about to publish "The Judy Blume Diary," complete with lots of room to confide in, elegant photographs of children taken by children, some advice on maintenance of privacy without locks and quotes from her books sprinkled throughout. ("Yes," she grins, "quotes from Chairman Judy.")

All royalties from "Diary" sales will go into a foundation she has set up called the K.I.D.S. Fund, designed to provide some funds to new community groups that have as their main function helping parents and children to communicate. A school librarian in South Carolina who uses Blume and other authors as subjects for joint parent-child group discussions appears likely to be the first beneficiary.

Blume's new book, "Tiger Eyes," is about Davey, an adolescent girl whose father is killed. It's about how the family almost breaks up and then comes back together. It's about dealing with death.

After she wrote it, Judy Blume realized that a lot of it was about herself. Her voice trembles a little as she says, "I adored my father. I think that Davey's love for her father, well, maybe it's the way I felt about it. That anger when you say, 'Don't be dead, Daddy. Please let it be a big mistake. I need you and I want you.' " Judy Blume's voice breaks.

"And you never really get over that. It is my theory that you keep someone alive by not being afraid to talk about it."

Judy Blume is really happy to be back in New York. And as she talks about it, her mobile face brightens, and the aching back is forgotten. She says, "Oh, Santa Fe is beautiful and everybody who comes there says, 'Oh, if only I could live there,' but after five years of living there I couldn't wait to get back to the city.

"I walk around New York and I'm like one of those crazy ladies -- I'm always singing to myself. I just can't get my fill of it."

From one of the letters to Judy Blume:

"How does the baby get in there and where does the baby come out?"

From another:

"Send me the facts of life, in number order . . ."

And another:

"I can't talk to my parents about personal things. I feel so alone . . ."