What are the major lessons in Chinua Achebe's Things Fall Apart?
Achebe's Things Fall Apart demonstrates the tumultuous consequences of colonialism, imperialism, and the western obsession with converting foreign tribes to Christianity, but it also warns against the dangers of hypermasculinity.
First, and more broadly, the novel is a colonial / post-colonial novel that, in part, depicts that process of change that occurs when foreign (western) cultures colonize other areas (such as countries and villages in Africa and Asia). There is, of course, some resistance to the Christian missionaries, but some villagers convert after buying into the rhetoric of the colonizers. The novel also illustrates how seemingly easy it is for dominant cultures to come into a less-developed area of the world and completely take over. The resistance of the tribesman, including Okonkwo, is ultimately futile. When the novel ends and one of the western characters sees Okonkwo's body hanging as a result of his suicide, he thinks about how this example will make a small part of his written work on "the pacification" of the tribes.
Second, Okonkwo's character is an example of how hypermasculinity can lead to tragedy. Okonkwo, in response to what he perceives as the weakness of his own father, goes to extremes to prove his masculinity. This includes killing a boy who is held hostage in his home but also has become part of his family. Eventually, Okonkwo is exiled because he commits a "female crime" when his weapon fires and accidentally kills another man. He must serve a seven-year exile in his mother's homeland. This should ostensibly teach Okonkwo the consequences of his extreme behavior, but when he returns to his village, he is aggressive and violent toward the missionaries. Okonkwo's behavior is viewed as extreme even by other male members of the patriarchal tribe.