What is the theme in Season of Migration to the North by Tayeb Salih?

One of the major themes of the book is the clash between Occidental and Oriental cultures. This is also referred to as North and South throughout the book. Both Mustafa and the narrator came from small Sudanese villages and were educated in England. Mustafa accepted and tried to become a part of the Western culture by running around with women. Many of the women around him committed suicide because of the lies he told them and because of the empty promises he made. He married one, Jean Morris, and admitted to killing her. He ends up returning to the Sudan and settling in a small village and marrying a local woman and living according to the village customs and traditions.