Things Fall Apart by Chinua Achebe is an example of a postcolonial novel that attempts to show the effects of British colonialism on the Igbo people of Nigeria. It is basically a historical novel, looking backwards to a pure Igbo culture, as it existed in villages remote from the initial colonial incursions and showing how those villages changed as Christianity and British rule slowly penetrated the interior of Nigeria.

The novel replicates the tension between the two cultures. In terms of genre, this is a novel written in English, both the language of the imperial British and a genre that is European rather than African. In using this form, Achebe is engaging in mimicry and showing how the Igbo have assimilated to British culture.

The use of native Igbo forms and material act as a site of resistance to that assimilation, articulating the vision of the subaltern culture. This blending is referred to as hybridity and both acknowledges the postcolonial nature of modern Nigeria while resisting the hegemonic nature of British colonial culture. 

A major theme of Chinua Achebe's novel Things Fall Apart is culture clash, or inter-cultural conflict generated by unprecedented interactions between two cultures. This theme is not only illustrated through the characters, syntax, diction, and plot of Achebe's piece, but also through the construction of the work itself. 

In traditional Western literature, there are certain expectations of the novel as a literary form. Characters and plots are meant to develop in a sure, expected manner; details are meant to be linear, clearly and pointedly developing one after another. 

This is sharply contrasted against Igbo cultural norms, which Achebe represents in his literature. Igbo culture, its proverbs, parables, and traditions, are perceived by Western characters, and indeed by many Western readers, as indirect, unnecessary, and frustrating. 

By integrating Igbo tradition into a Western literary form, Achebe's novel embodies this major theme of his work, culture clash.