By ALICE DIGILIO THE PEOPLE IN PINEAPPLE PLACE, by Anne Lindbergh (Harcourt Brace Jovanovich, $10.95. Ages 9-12). August Brown is a 10- year-old boy in an unenviable position. His parents have just split up, his mother has started a full-time job, and he's recently moved with her to Washington where he hasn't any friends. The final indignity--his old buddy up in Vermont where he used to live, still owes him $4.79, which he'll probably forget to repay.

Bored, confused, and hurt, August is eager to escape. And he does, in this deft novel about adjusting to new things. Wandering around his neighborhood in Georgetown, August meets a whole street (Pineapple Place) full of people, including six children and several fascinating adults. The odd thing is, no one but he can see them.

Lindbergh skillfully moves August back and forth between his two worlds--the one he shares with his mother, and that of Pineapple Place, which is his private preserve. Eventually, the two worlds meet, and there is a happy resolution to August's unhappy situation. With the help of April, his favorite among the invisible friends, he makes a visible friend. And that, after all, is what he needs most.

For a slim novel, The People in Pineapple Place covers a lot of material, including some historical background on Georgetown. But one never has the sense that Lindbergh has piled her plate too high. She draws her characters--both the children and the adults--sharply and well, and always writes with a gentle sense of humor --all of which makes for a very successful novel.

THE WILD BABY GOES TO SEA by Barbro Lindgren, illustrated by Eva Eriksson, adapted from the Swedish by Jack Prelutsky (Greenwillow, $9.50, Ages 4-8). Pug-nosed Wild Baby Ben is the hero for a series of books about a toddler and his make-believe adventures. In this one he sets off to sea in a wooden box, propelled by a floor brush paddle and sail made of his mother's apron. He enlists as crew his favorite stuffed animals--"Mouse, Giraffe, and Bunny too." Engulfed by heavy seas, plagued by ferocious fish and monsters from the deep, even capsized at one point, the little company perseveres, and Ben brings them safely home again.

Lindgren has an excellent sense of what a child's imaginative play is all about. Like Max in Where the Wild Things Are, Ben is hero, and triumphs over forces more powerful than himself. He plays at being adult, in control of what happens to him. Yet when things get out of hand, he can call off the voyage, and return to the safety of Mother and a lunch of fried eggs. He and his crew--and his long-suffering Mother who obviously encourages Ben's exploits by providing most of the necessary equipment and provisions--are all drawn by Eva Ericksson with care and whimsy in a series of highly detailed pastel cartoons.

NEXT PANDA, PLEASE! Further Adventures of a Wildlife Vet, by David Taylor (Stein and Day, $12.95; Ages 12-up). Although not written especially for young people, David Taylor's new book will interest many of them--particularly those who can't get enough to read about dolphins, pandas and such. For Taylor is the veterinary equivalent of a shuttle diplomat. His flight bag packed with a mind-boggling array of medicines and equipment, Taylor is ready to fly anywhere in the world at the ring of a telephone. His patients can be, and have been, anything from armadillos to zebras, and he's treated them under all sorts of conditions.

"Veterinary medicine isn't 'Animal Magic' crossed with 'Dr. Kildare.' it has much more in common with the blood and guts and pain of front- line battlefield surgery," writes Taylor about his work. Indeed, from his fast-moving narratives of encounters with Salmonella, Pseudomonas bacteria, Aspergillus fungus, as well as a variety of injuries suffered by animals, one does get the impression that he lives constantly on the edge of crisis. Many of his patients reside in less than ideal circumstances--in traveling animal shows, movie sets, safari parks. And, as he tells us, some of their health problems are caused by their environments. But Taylor is not a preacher. His main concern as a veterinarian is to cure animals, and as a writer it is to explain how he does so with as much clarity and humor as possible.

There are some very funny scenes in the book, such as the time when Taylor, equipped with hip boots and medical bag, examined an enormous partially submerged elephant seal in front of French television cameras. The animal threw away his bag, grasped Taylor in a suffocating bear hug, and then tossed him about. Taylor's response of expletives were translated into French as, "Dearie me, this chest sounds a bit rough" and "Isn't he a lovely old fellow. I enjoy doctoring elephant seals."

Children will appreciate Taylor's ability to laugh at himself, and they doubtless will love his slightly corny slapstick humor in this altogether delightful, and instructive, memoir.

CECELIA AND THE BLUE MOUNTAIN BOY, by Ellen Harvey Showell, illustrated by Margot Tomes (Lothrop, Lee and Shepard, $9.50. Ages 9-up). We have here a story within a story, as a boy who's come to compete in a music contest in a tiny mountain town is told by two mysterious children how the competition got its start. There are echoes of fairy tale themes here--the quest for the impossible, enchantment. There's even a hint of The Red Shoes.

Cecelia is a child who cannot bear to live without music and dance, but her family and village don't countenance such things. One day on a search for the elusive music she hears continually in her head, she finds Blue Mountain, and a fiddler boy named Daniel who is the source of the mountain's music, and it seems, the tunes she has always heard. She wakes from her dream--if it is a dream--and from there on,,Cecelia's life becomes a frustrated effort to relive her experience on Blue Mountain.

Ellen Harvey Showell's story has a bit of the shaggy dog about it. It sometimes seems as circuitous as some of the mountain tunes country fiddlers play. Consequently, Margot Tomes' striking black and white illustrations give it some needed unity and continuity. Together the text and illustrations make a very attractive combination, gracefully conveying the rhythm and sense of mountain life.

CARS AND HOW THEY GO, by Joanna Cole, illustrated by Gail Gibbons (Crowell, $9.95. Ages 7-11). In this clearly written, colorfully illustrated book, a very complicated machine is made understandable. Beginning with the horse-drawn carriage, the authors first establish how wheels turn, then go on to divulge, in logical sequence, the intricacies of the internal combustion engine with its cylinders, crankshaft, pistons, and so on. Gail Gibbon's diagrams, done in primary colors, are as illuminating as Joanna Cole's text is clear.

Although it doesn't tell how to change the oil, Cars and How They Go will answer the questions of almost any child curious about why the car starts when the key is turned.