The theme almost takes over the whole novel, and several marriages are being contrasted. Would you say that Mrs Bennet's marriage with Mr Bennet is a happy one? How does Austen define a good marriage in her novel?
Happy is a pretty subjective term for the times. The Mr. and Mrs. Bennet were products of a painfully rigid class structure. Wealth eluded them so from that point, and it is a major one, they were not happy. Still they were together and seemed to understand one another which is saying quite a bit. Austen is critical of the gender injustices present in 19th century English society. The novel demonstrates how money such as Charlotte need to marry men they are not in love with simply in order to gain financial security. The entailment of the Longbourn estate is an extreme hardship on the Bennet family, and is quite obviously unjust. The entailment of Mr. Bennet's estate leaves his daughters in a poor financial situation which both requires them to marry and makes it more difficult to marry well. Clearly, Austen believes that woman are at least as intelligent and capable as men, and considers their inferior status in society to be unjust. She herself went against convention by remaining single and earning a living through her novels. In her personal letters Austen advises friends only to marry for love. Through the plot of the novel it is clear that Austen wants to show how Elizabeth is able to be happy by refusing to marry for financial purposes and only marrying a man whom she truly loves and esteems.
http://www.gradesaver.com/pride-and-prejudice/study-guide/major-themes/
