A PROBLEM with reviewing Superfudge was getting the book to stay still long enough to read it. The bush telegraph of 8-and 9-year-olds somehow got the word that Fudge was back. Peter Hatcher and his impossible kid brother have friends and fans everywhere: the children who empathized and chuckled their way through Tales of a Fourth Grade Nothing, as Peter's comfortable life in a Hatcher's Manhattan apartment was turned upside down by a living 2-year-old tornado known as "Fudge."

They had groaned and gasped when the ultimate happened -- Fudgie ate his brother's adored pet turtle -- and now they couldn't wait to see how Peter had survived another year in the Hatcher household. Many of them found out before I did, but when finally the door was locked and the book in hand, Peter was discovered entering sixth grade. He has moved, at least for a year, to the suburbs -- Princeton in fact.

Judy Blume, however, knows better than to let Peter spend a quiet year breathing cleaner air. Mrs. Hatcher produces ("How could you?" cries Peter) a second sibling known as Tootsie, Mr. Hatcher tries to write a book, and Peter goes into the worm business with his new friend, Alex.

Judy Blume's book for younger readers are funny, in just the outrageous way that appeals to the broad humor of 8- to 10-year-olds, but even more important to children is the clear knowledge that Blume is on their team. She doesn't tell them about Mommies who must work to fulfill themselves or parents who know it all or that one must be patient with pesky smaller kids. Peter is often driven to exasperation at the denseness of his grown-ups: no one seemed to care about the fate of his turtle as they waited at the hospital . . .

This subversive position enslaves children. Adult readers find it cute in books about 8- and 9-year-old urchins, but Blume's reputation -- or notoriety -- is so bound up with her novels for teenage girls that many forget she can create good clean fun. Peter is preocupied with his turtle, selling worms and persuading Fudge to come down from the top of the kindegarten closet. Margaret of Are You There God? It's Me Margaret is 14 not 10, a girl not a boy, and is therefore more preoccupied with grow-bras and the onset of menstruation. The furor about novels like Margaret and Blubber (children do persecute overweight contemporaries whether or not Judy Blume writes about it) assuredly hasn't decreased her audience. There is no more determined reader than he or she who has been forbidden a certain volume, and no underground distribution network works like that of the playground. All the same, Superfudge will come as a relief to those who are made nervous by the very sound of the name Judy Blume.

Superfudge suffers from many of the problems typical of sequels. Its hard to top Fudge's exploit of eating the turtle, Fudge himself is older and the helpless Tootsie isn't yet very interesting -- in fact on occasion the intrepid Peter seems almost to fall prey to her innocent charms, to forget that this bundle is an embryo Fudge. Fudge himself does acquire a most talkative mynah bird called Uncle Feather who helps the action along, but on the whole this is a book for the friends of Peter Hatcher -- and they are legion.