In order to write such an essay, you need to decide on a specific theme on which to focus, or a specific critical approach to use. One possible focus would be narrative voice. You could examine how the third person narrator sets the tone of the novel and guides the reader`s attitude towards the protagonist. (Wayne Booth is a good guide to analyzing narration) Another possible approach would be feminist analysis in which you consider how oppression of women creates the preconditions for both novels. You might also choose to do a form of Marxist literary analysis and look at how the rise of the bourgeoisie affected the institution of marriage and led to the alienation of the wife as worker.