The grass is singing / Doris Lessing.

Enhanced descriptions from Syndetics:

Set in South Africa under white rule, Doris Lessing's first novel is both a riveting chronicle of human disintegration and a beautifully understated social critique. Mary Turner is a self-confident, independent young woman who becomes the depressed, frustrated wife of an ineffectual, unsuccessful farmer. Little by little the ennui of years on the farm work their slow poison, and Mary's despair progresses until the fateful arrival of an enigmatic and virile black servant, Moses. Locked in anguish, Mary and Moses--master and slave--are trapped in a web of mounting attraction and repulsion. Their psychic tension explodes in an electrifying scene that ends this disturbing tale of racial strife in colonial South Africa.

The Grass Is Singing blends Lessing's imaginative vision with her own vividly remembered early childhood to recreate the quiet horror of a woman's struggle against a ruthless fate.