The satirical nature of the book is the unfolding of the events in the book.
We anticipated Sidi would be married to Lankule and not Baroka whom she despised.
Baroka lied to his eldest wife, Sadiku that he was impotent. Sadiku, happy at the good news of her husband's impotence rushes to tell Sidi.
Sidi doesn't think twice despite knowing the cunning nature of Baroka. She decides to visit Baroka with the intention of mocking his impotency.
What happens? Her mission to ridicule Baroka turns into mourning. Baroka has deflowered her.
Satire is the use of humor, sarcasm, irony, or ridicule with the intent of showing fallacy or vices committed by an individual, society, or government.
Which fallacy or vice was being criticized or disproved? The fallacy of Sadiku, a gossiper, and Sidi, a proud girl.
In the end, the writer points out that gossiping and being proud are vices that aren't acceptable in the society.