This novel is, by far, Jane Austen most ironic and wittiest writings - which is probably why it is her most well known. She uses ironic statements throughout her narration to comment on social behaviors in her world. The novel begins with one such statement:
"It is a truth universally acknowledged that a single man in possession of a good fortune must be in want of a wife."
The generalization and the assumption in this sentence - that all people know that a single rich man must want a wife - is humorous and sarcastic. She is attacking the attitude of society that sees this man as a possession to be grasped by the most enterprising mothers and daughters.
It is not only in the narration that Austen uses wit. Her most admirable characters in the novel are those that are themselves witty. Mr. Bennet, for example, is described as thus:
Mr. Bennet was so odd a mixture of quick tarts, sarcastic humor, reserve, and caprice, ....
While he has his faults, readers are meant to admire this sarcastic man - and thus, to admire the way in which he shuns the standards of society.
Elizabeth Bennet, the hero, is also a witty character that uses irony to her advantage:
she had a lively, playful disposition, which delighted in anything ridiculous.
I don't have time to go into the situational irony that occurs in the novel, but suffice it to say that wit and irony are both plot developers and character developers in this story.