The awesome, living heart of the Amazon rain forest is the draw of this simple, didactic novel of survival. Allan Eckert, a naturalist, prolific writer and Newberry Award winner, paints a strong, authoritative picture of the forest in the grandeur of its unity and the incomparable denseness and richness of its detail, though much of the time his characterizations and story line have all the subtlety of "Wild Kingdom."

It is hard to guess why this book is designated a novel for adults, when it seems within reach of a reader of 10 and a fine tale for children (especially girls) a few years older -- like its heroine, Sarah Francis. Sarah, whose parents are divorced, has, after a couple of miserable years with her mother, settled in comfortably with her father, an archeologist -- quite a teddy bear of a dad, justifiably confident of his daughter and given to kissing the end of her nose.

Because Sarah is so resourceful, reliable, observant and level-headed, she is permitted to accompany her father on an important dig in the jungles of Brazil, 60 miles from the nearest settlement, traveling by canoe on gradually narrowing rivers lined by crocodiles. The final, utterly trackless eight miles the party must labor overland, unescorted, for the ruin is known to turn back, if not kill, all who venture to unveil its secrets.

Sure enough, within weeks all but three of the party have been stricken with a sickness so virulent that the decision is made to trek back in search of help, leaving Dr. Francis and Sarah to guard the site until their colleagues can rejoin them. On their third day alone, Dr. Francis is on the verge of a tremendous breakthrough. He's wormed himself halfway into a deeply buried chamber and is excitedly calling back to tell Sarah what's in there when the huge block of stone in the archway directly over him crashes down.

Sarah copes well with seeing her father crushed before her eyes and being left alone in a treacherous wilderness. She digs frantically for her father, but when at last her fingers find his broken head, the raw horror fades away and is supplanted by a suitable healthy grief. The following dawn she orders herself to stop trembling and "Think: What would Dad want me to do?" She buries him and, carrying the barest necessities, sets out in hope of meeting up with the rest of the expedition. A stone's throw from camp the going is already getting rugh as Sarah enters the other world of the rain forest. She has no compass, and in an hour she is irremediably lost.

Now Eckert seems really in his element, describing the wonders of this forest -- the "leafy canopy" of trees towering up 200 feet: the great woody vines called "lianas" twisting, hanging, trailing, fallen, creaking, groaning and eerily singing; the ever-moldering forest floor with its mossy boulders and 10-foot-high ferns -- like a "vast, endless cathedral, where light and sound were muted" and every step mined with astonishing flora and fauna, all remarkably beautiful, large, ugly, life-threatening..

The trouble is that while the author is painstakingly concerned with how Sarah must strain her body and wits to survive, he undervalues the serious, reverberating impact of her father's horrible death. What happens is that the emotional possibilities of a novel coagulate into an adventure story and nature walk punctuated with positive-thinking, health-classlike words about Sarah's chunky but developing figure, her pubic hair and her first menstrual period. Pep talks of Dad's float back to Sarah, recharging her with "intestinal fortitude -- plain old guts," "stick-to-itiveness" and so forth.

After more jungle adventures, Sarah ends up in a village, where she gains acceptance as an honorary member of the tribe. This entire long stretch of the book is packed with lore about blowguns, wild beasts, white water, witch-doctoring, head-shrinking and more.

Sarah finishes her odyssey, learning that the strange customs of the "savages" have a natural logic, directness and simplicity that "civilization" could use more of -- a simple lesson but not at all a bad one. The same might be said of the book.