An imaginative, poetic and often amusing story, written with great skill, this successfully treads that thin line that wavers between fantasy and realism. The hero of the story is a blue kitten, born under a blue moon, and living near a small Vermont town in the time of our Revolutionary War. Because he is blue, he is privileged to know the song of the river, and it is his destiny to seek out a friendly hearth and inspire his owner with the beauty and wisdom and truth that lie in the river's song. This is an allegory concerned with the struggle between truth and sincerity and shoddy pretense and greed. The cat is a real personality. Young readers will remember long the purring wisdom of his song and be fascinated by the colonial, historical characters in the old town about which the author weaves her tale. And children within reach of New York's Metropolitan Museum of Art will want to see the American tapestry from which the legendary blue cat of contentment gazes out. An unusual and lovely book which could so easily have degenerated into sentimentality, but which sets and holds its own pattern. A book adults will enjoy reading with children of six to eight.