"Lost in the Stars" is based on "Cry, the Beloved Country" by Alan Paton, but it is a musical adaptation of the novel, not a direct retelling. The musical retains the story's themes of racial injustice and the struggle for a better future in South Africa, but it uses music and song to tell the story.
While both the novel and the musical deal with similar themes, the musical is a different creative interpretation of the source material.