MUCH OF THE BEST writing for children has beenabout small creatures who live surrounded by large ones. Since that pretty well describes how children themselves live, the appeal is a natural one.

Sometimes the small beings are animals and the large ones people, as in Margery Sharp's wonderful series about the elegant white mouse Miss Bianca, her human "owner," her humble whiskery follower Bernard, and the Mouse Prisoner's Aid Society. Sometimes the small ones are people and the large ones some bigger race, as in "Jack and the Beanstalk," alias "Jack the Giant-Killer." Sometimes the smaller creatures are fairies, elves, gnomes and dwarves, and the large ones men. Occasionally the small ones are miniature human beings--living dolls--and the large ones people of the usual size.

Probably the most famous example of this last genre (unless you count Gulliver's Travels itself, and you shouldn't, because it wasn't written for children) is Mistress Masham's Repose. T.H. White published that small gem in 1946. In it, a colony of Lilliputians, brought back to England in Swift's time, long ago escaped, and has been living for many generations on an island in a lake on a ducal estate. An orphaned little girl of the ducal family and a wicked clergyman rediscover the colony more or less simultaneously, and sharp adventures follow.

Much cozier and perhaps a little cuter than White, but really just as good, is Mary Norton's series of books about the six-inch-tall people called borrowers. She may be cozy, in a Dorothy Sayers-Miss Reade-Lord Peter Wimsey sort of way, but she entirely avoids White's gruff sentimentality. She is fully his equal at adventures.

The Borrowers Avenged is Norton's sixth book about her small people. It is a pleasure to report that it holds up to the other five. There are no signs of infectious sequelitis here. One reason may be the author's restraint. The Borrowers itself came out in 1952--and five sequels over a 30-year period is hardly a rush to cash in on success.

As usual, the main characters are Pod and Homily, the father and mother in a borrower family, and Arrietty, their half-grown daughter. (She must be quite five inches tall.) As usual, the setting is Little Fordham, one of those gentle English villages where life revolves around the church and the manor house. And as usual the time is that golden moment in English history just before World War I, when all was right with the world.

All hasn't been right for Pod, Homily, and Arrietty, however. Like other borrowers--and like mice, for that matter--they are heavily dependent on what they call human beans. They live in human houses, often in neat apartments under the floor, and they get their food supplies from our kitchens, using their borrowing bags. They also take the occasional needle or handkerchief (to make into sheets) or thimble, which is why human beans so often think they have lost these small items. And their first law is to stay out of our sight and hearing.

Pod, Homily, and Arrietty have done much worse than be seen. A book or two back, they were captured by Mr. and Mrs. Platter, who intend to exhibit them in a model village, so constructed that they will have no privacy night or day. As the new book begins, they have just escaped, and are in the process of moving by boat to a new house. It's a far grander one than they have ever lived in before, being the Old Rectory in Little Fordham.

With great skill, Norton develops two stories, which mesh neatly in the climactic scene at the end of the book. One story involves the human beans, and especially the persistent attempts of Mr. and Mrs. Platter to recapture their victims. The other and principal story is, of course, Arrietty's. She is growing up. In the course of the book she gets her own borrowing bag and learns to go on expeditions. She and her parents fit up a marvelous house under a windowseat in the rectory library. She finds long-lost relatives living in an old harmonium in the vestry of the church. Most exciting, she meets a young man about her size named Peregrine Overmantel, the last survivor of a distinguished borrower family long resident in the rectory. (One characteristic of borrowers is that they have slightly mangled human names, and Peregrine's flawless name is a mark of his upper-class status. Pod and Homily promptly convert it to Peagreen.) At the end of the book, the Platters make a last and desperate attempt, in the church itself, and fail.

What gives the book its charm is a combination of several things. One is the completely believable psychology of the borrowers. Unlike elves and so forth, they have no magic or special powers of any kind--they have to get on unaided, just as we do. Unlike all human beans except small children, they are pleasingly free of conscience. They are intellectually simple, emotionally complex, and utterly delightful.

Another is the dialogue. Like borrower names, borrower speech is slightly mangled--for all but Peregrine, a slightly mangled version of lower-class English rural speech, complete with the pithiness. It makes good reading.

A third is the consistent ingenuity with which borrowers turn human artifacts to their own purposes. It's the same pleasure one gets in watching Robinson Crusoe set up housekeeping with what he can salvage from the wrecked ship, but intensified from the tiny scale.

Finally, there is an element contributed not by Mary Norton but by Beth and Joe Krush, who drew the 33 illustrations. Mrs. Krush, a native of Washington, and her husband have illustrated all the borrower books, and they have done distinguished work right along. But here, in layout and technique both, they have surpassed themselves. Their drawings are sort of Dickensian miniatures, but without the touch of caricature. Arrietty herself is the best of all. In fact, it is a little frustrating to find oneself feeling fatherly about a girl who is five inches tall and lives under a window seat in an English village in 1911.

The only solution is to read the book aloud to some small human bean.