OCCASIONALLY, not often enough, in the world of young people's books - or anyone's - there appears a timeless work which defies delimiting of audience. Such a book is Anpao, a synthesis of native American folklore, and an Honor Book for this year's Newbery Medal. Jamake Highwater, of Blackfeet/Cherokee inheritance, is an author of works for adults, including Fodor's Guide to Indian America. He is a cultural anthropologist and an honorary member of the White Buffalo Council of American Indians, an intertribal organization.

He has woven across the main threads of his legendary hero's guest a significant weft of American Indian mythology, just as Homer in his famous epic of a Greek's journey homeward from Troy introduced tales of supernatural encounters which extended the dangers of that voyage.

None of these tales, says Highwater, is of his own invention, altough the words are new, his own. Most exist in many versions, but in his meticulous biliography of sources he cites at least one book in which each tale can be read in its oral form. Some of these are ancient; soem emerged out of experiences after the invasion by white men.

The illustrator, who is of Luiseno Indian blood, has provided an evocative jacket painting and four impressionistic stone lithographs - of owl, buffalo, bat, and death - which he calls mysterious and magical subjects.

The central connective theme if the Blackfeet Scarface legend written down long ago by George Grinnell, famous anthropologist-recorder of Indian lore. Anpao, modeled on Scarface, son of the Sun and a human mother, is in love witha maiden claimed by the Sun. Building on this, Highwater has created a kind of chronicle of the Indians of America, including material from a number of Indian boyhoods.

His hero journeys through Indian history, challenged by the beautiful Ko-ko-mik-e-is. She has rejected all the rich and handsome and brave suitors but is willing to marry Anpao if he will tell the Sun of his desire to marry her. If the Sun will also remove the scars from Anpao's face, it will be a sign to her that they may marry.

So, in season after season of arduous travel, Anpao meets many different tribes with diversified cultures and customs. Some of his adventures are recounted as complete stories in themselves, like the Cheyenne tale of "Snake Boy" who eats the large greenish eggs of some unseen creature and turns into a serpentine water-dweller. A creature story, "The Dawn of the World," also comes from the Cheyenne. Here Highwater's poetic narration begs to be read aloud: "At the place where all things began, there was first the black world. And Old Man, the all-spirit, lived in this void, silently a and without motion. For he was he. . . Because he was everything, Old Man was not lonely. But as he radiated through the endless time of nothingness, it seemed to him that someting might be more interesting than nothing."

There is a time later when Anpao discovers buffalos and encounters sorcerers. The sorcerer who came up with animals, through a hole in the earth's surface, "remade all the people into their own image so that they could safely hide among people without anybody ever realizing it. Ever since that day sorcerers have secretly lived among men, unrecognized because they look just like other people."

Passages like these show that not only the uniquences and significance of the content make this an enduring book, but also the author's gift for using the poetic, dignified language required of tellers of great epics.