Realism in literature falls into two categories: realism of content and realism of presentation. Realism of content is when the literature is true to life. Much of Pride and Prejudice is true to life. The situation of the family in regards to their wealth and status, the problems the girls have securing a good husband, the attitudes and behaviors of the characters themselves - all of that is true to life. However, the "coincidences" that occur to bring all the characters together are too easy, and therefore not really true to life.
This is where realism of presentation comes in. In reference to presentation, realism is defined as bringing something close to reality or to the audience through the use of sufficient description. This is how Austen solves the realism problem. She develops the characters so complexly that audiences believe each and every action, even Darcy's "act of heroism" in regards to Lydia and Wickham. With the use of character monologues, explanatory letters, and narrator explanations, Austen sufficiently identifies the motives of each character. Moreover, the characters themselves accept the reality of what is happening to them. If we accept the character's reliability, then we must accept their perception of their own world.
C.S.Lewis in his book "An Experiment in Criticism" (1992) defines Realism of Presentation as:"the art of bringing something close to us, making it palpable and vivid, by sharply observed or sharply imagined detail."(P.57).
The best example for Presentational Realism would be Ch.43 of "Pride and Prejudice" in which Jane Austen presents to her readers a very realistic description of the Pemberley estate and Pemberley House. The precise measurement of the extent of the estate is specified: "it was ten miles round."
In p.59 of his book Lewis emphasizes the subtle difference between Presentational Realism and Realism of Content. He defines Realism of Content as, "a fiction is realistic in content when it is probable or 'true to life' "(p.59).
Thus Presentational Realism would, according to C.S.Lewis, be the 'how' and Realism of Content the 'what' of a novelist's craft.
Needless to say, the universal appeal of "Pride and Prejudice" is mainly due to the fact that the incidents and characters are 'probable' and 'true to life.'
In "Pride and Prejudice" Jane Austen deals with the universal institution of marriage and all its related issues-reasons for marrying; the importance of money, status and prestige; happiness or lack thereof in marriage.