True story gives example of some of motherhood's best qualities; Eleni, by Nicholas Gage. New York: Random House. 471 pp. $15.95.

Eleni, the real-life heroine of this superb book, was the mother of the author, Nicholas Gage. His account of his family's life and his mother's death at the hands of Greek communist guerrillas after World War II tells in vivid terms of the power of a mother's love. Eleni is no idealized saint, but her devotion to her children's survival is an example of motherhood's very best qualities.

Much of the book takes place in Lia, a village near the Greek-Albanian border. Many villagers had never been out of the general vicinity, but Eleni's family was different. Christos, her husband, had emigrated to the United States. His hard work enabled him to send money and gifts to his family. Hoping to join him someday, Eleni shared her abundance with neighbors who admired and envied her.

War, first with Germans during World War II and later between communist guerrillas and government forces, changed their relatively simple lives. Eventually the Greek communists took control in Lia. As conditions worsened, the communists separated young children from their families and sent them into exile in Albania and other communist countries. Older female children were forced to join the guerrillas. Realizing that her son and four daughters would soon be sent either into exile or to fight with the communists, Eleni arranged for a neighbor to help them flee.

Two escape attempts failed. Then one daughter was conscripted to cut wheat for the guerrillas. When another ''volunteer'' harvester was needed, Eleni went. But she made the remaining youngsters promise to escape, to contact their father , and then to make their way to America.

The children and some other villagers succeeded in getting out, but the fact that 20 people had evaded capture infuriated the communists. They began looking for scapegoats to use as examples, and fear turned many villagers into informers against their friends - innocent and guilty alike. Ultimately, Eleni and four others were tortured and then put to death. But all her children - including the one taken to harvest wheat - were saved.

This brief outline barely hints at the book's excellence. Moral courage, kindness, intelligence, and love pervade its people. Despite the usual human failings, many of the villagers proved extraordinarily brave when put to the test.

Nor is the book just a record of sorrows. Among the lighter touches is Nicholas's attempt to build a swimming pool. At six years old, he had heard of, but never seen, this wonder described by his father in America. One hot day he dug the biggest hole he could and then spent two hours trying to fill it with water, which just seeped into the ground. Finally, there was about two inches of mud in the bottom. Although that didn't look like what he had envisioned, he took off his outer clothes and plunged into the hole head first.

A neighbor happened to see his mud-covered figure sticking out of the ground and thought it was a demon. Her screams brought the neighbors running to see the boy doing ''his best at what he thought must be the backstroke.''

Nicholas Gage was a reporter for the New York Times for a decade before quitting his job to tell his mother's story. He interviewed scores of people - villagers, soldiers, government officials - and read voluminous reports and other documents. In the beginning, he wanted to avenge Eleni's death. But writing the book and seeing how his mother refused to hate even her enemies showed him that revenge would never break the cycle of killing.

Gage's account of her life is more than the story of one person. It tells in a powerful way how a mother's love can reach far beyond the limitations of time, space, and even death to save and protect her young.