It's not clear from the novel where the events actually take place -- no country is actually named. We are to understand, I guess, that the novel is set in a "modern west African nation" -- possibly Nigeria -- but that is as specific as it gets. More significant for the action of the novel in terms of setting is the bush/city dichotomy -- the bush representing traditional African society, and the city representing Westernization, political power, and corruption. I don't think it's true, though, to assert that the bush is somehow more "African" than Bori, the capital city. The fact that Nanga seems equally comfortable in either place suggests that perhaps, despite his corruption and will to power, he really is "a man of the people."
A Man of the People by Nigerian novelist Chinua Achebe was first published in 1966. The author himself was a member of the Igbo tribe, and also a strong supporter of the Biafra independence movement, which was going on as he wrote the book.
The setting of A Man of the People is an African country that is not actually named. The main events in the book contrast the rural areas or "bush" with the urban capital. Within this novel, the bush represents African traditions, including polygamy, and tribal society. The city is the center of political power, and more deeply corrupted by imperialist influences. As the novel is a satire, though, the bush is not associated with primitivist innocence, but rather with its own small scale feuds and crimes.
The city is home to political power and graft, but also the educated classes who resist such power. The narrator, Odili, initially plans to teach in the bush to escape the political corruption in the city, but is drawn in by its centripetal force.
Achebe summarizes the graft and corruption present in the city, and the difficulty of maintaining personal integrity in the face of it, by saying:
Tell them that this man has used his position to enrich himself and they would ask you –as my father did—if you thought that a sensible man would spit out the juicy morsel that good fortune placed in his mouth.