So Long a Letter was an instant critical success, winning the Noma Award for Publishing in Africa. Despite her premature death, Bâ is seen as a major African writer. Her slender first novel, while popular (it was translated into sixteen languages), has also been at the center of controversy. Critics are not sure what to make of Bâ's politics. Some call her a feminist, but others think she betrays feminism. Some are proud of her distinctly African literary voice, but others think she caters to Western values. Some see her envisioning unity across the classes, but others find her novels elitist.

Much of the controversy surrounding Bâ's novel springs from the controversy surrounding Islam and polygamy in Africa today. Ramatoulaye, after all, as the narrator of So Long a Letter, presents herself as a victim of polygamy. This stance draws the critical attention of those who seek to defend polygamy and those who see, with Ramatoulaye, polygamy as a violation of women's rights. Critic Ella Brown, for instance, sees the novel as a condemnation of Islam: ‘‘It is obvious that [Ramatoulaye's] religion is the cause of the many ills she complains of. Her life would be much happier in a society that gave greater consideration to the needs of women.’’ Dorothy Grimes, however, argues that "it seems Mariama Bâ, in the persona of Ramatoulaye, would have women also seek to reclaim traditional custom and thus to redefine it.’’ In other words, Grimes does not believe Bâ would want to abandon the old traditions but rather transform them for a changing world. Edris Makward, meanwhile, calls Mariama Ba "the first African woman to stress unequivocally the strong desire of the new generation of Africans to break away from the age-old marriage customs and adopt a decidedly more modern approach based on free mutual choice and the equality of the two partners.'' Other critics, such as J. O. J. Nwachukwa-Agbada and Audee Tanumu Giwa, however, believe that Bâ does not present either Muslim religious beliefs or polygamy accurately.

In his article, '‘‘A Feminist Just Like Us?': Teaching Mariama Bâ's So Long a Letter,’’ John Champagne outlines some of the difficulties of teaching Bâ's novel in American classrooms. American students tend to identify with Ramatoulaye's outrage at her husband's polygamy. Seeing Ramatoulaye as ‘‘one of us,’’ the students read the novel as a critique of Senegalese and Islamic traditions and as supportive of American values. But as Champagne argues, to read the novel this way ignores its foreignness and difference, for, as Champagne points out, ‘‘at times, So Long a Letter is virtually unintelligible to a Western audience unfamiliar with both the history of Senegal and Islam. This is particularly true of the opening sections of the novel, in which the rituals surrounding the burial and mourning of Ramatoulaye's husband are described.’’ As Champagne argues, however, his students who ignore the historical specificity of Bâ's novel are no different than the many critics who ‘‘have in fact praised [the novel's] appeals to universalism and global feminism.’’ The best way for a Western reader to approach this novel, according to Champagne, is to cultivate an awareness of ‘‘the hybridity of Senegalese postcolonial culture.’’ In other words, the best reader of So Long a Letter will recognize Bâ's debt to the historical forces that have shaped modern Senegal. Champagne's article also suggests that the controversies surrounding So Long a Letter have as much to do with the critics' various subject positions—their nationality, gender, and religion—as with the novel itself.