Cry, the Beloved Country is a complicated coming-of-age story for one big reason: our main character Kumalo is already technically of age. In fact, he's quite elderly—we know that his hair is white. But in terms of Kumalo's knowledge of the dangers and temptations of city life, he may as well be a child. And Kumalo's rough introduction to Johannesburg means that he has to learn fast.
By the end of Cry, the Beloved Country, Kumalo has grown sadly familiar with the miseries of urban life. And he takes definite steps to improve the circumstances for the farmers of Ndotsheni, so that he can help preserve the country life that he believes is best for his people. So even if Kumalo's coming-of-age has come a bit late in his actual lifespan, he still gets an education in the ways of the world over the course of the novel, which transforms his outlook on reforming South Africa.
Not only does this novel represent a coming-of-age for Kumalo, but it's also a family drama for both Kumalo and Jarvis. While the larger backdrop of Cry, the Beloved Country is, of course, the social and racial inequalities of 1940s South Africa, the family provides the specific framework that Paton uses to show these inequalities.
So Kumalo's brother, sister, and son all disappear into the city to face various different kinds of moral temptation. His sister falls into lust, his brother into pride, and his son into greed. And Absalom's greed is what takes James Jarvis's son from him too soon. But in spite of these bitter family relations, Jarvis and Kumalo manage to find common ground between them in their desire to improve life for the people of Ndotsheni.
Last but absolutely not least, Cry, the Beloved Country is a tragedy. In spite of Kumalo's efforts to bring his people back together and to reinforce their moral values, Gertrude runs away, John continues to give his dangerous speeches, and Absalom is executed.
But there is a ray of hope in the middle of all of this sorrow and wasted life: Kumalo's grandson will be raised in Kumalo's home village, Jarvis has helped to bring agricultural reforms to Ndotsheni, and someday, racial relations will improve in South Africa. The immediate events of the novel may be tragic, but Cry, the Beloved Country also looks forward to a better future for the nation of South Africa as a whole.