"So Long a Letter" is an epistolary novel that explores the life of a recently widowed woman in Senegal. Throughout the story, she reflects on her life, her marriage, her husband's second, younger wife, and the status of women in Senegalese society. The book delves into themes of polygamy, friendship, and the struggle for women's rights in a predominantly patriarchal society. It is a poignant examination of the personal and cultural conflicts faced by women in post-colonial Africa.

The novel revolves around a middle-aged man who, after his twin brother's accidental death, is left to take care of the family farm and his ailing father in the Dutch countryside. Trapped by duty and familial expectations, he struggles with loneliness and the burden of an unfulfilled life. The narrative delves into themes of isolation, identity, and the profound impact of family dynamics as the protagonist grapples with his past and the stark reality of his present circumstances. The story unfolds against the backdrop of the stark, flat landscape, mirroring the protagonist's internal desolation and longing for a different existence.