What are the elements of literature as related to Romeo and Juliet?

Literature is written to produce an emotional response and a combination of elements work in concert to produce that effect. At their best, writers develop engaging plots that hold our interest while creating suspense, develop memorable, compelling characters that we care about, and use language and setting to create a mood. All works of literature also have a theme or point, even if that theme is pointlessness.

Shakespeare in Romeo and Juliet uses the well-worn plot of star-crossed lovers and infuses it with life. Both Romeo and Juliet are young and attractive, on fire, and use rich language to describe their feelings. They click instantly and want to be together forever. We care about these two and the dilemma that their families are locked in: a feud that means the two can't think about being openly together. This conflict catches our interest: how will the two lovers resolve it? The opposites that are juxtaposed are almost unfathomable: how can so much love and hate coexist side by side?

Shakespeare also establishes the theme of the futility of feuding from the start of the play. These families are killing each other and we as audience become engaged in this issue, for most of us have, one way or another, been part of arguments whose beginnings we can't begin to trace. 

From Romeo and Juliet to the nurse and Mercutio, Shakespeare has assembled a realistic and engaging set of characters. We care about the lively, fun-loving Mercutio--and because Mercutio is such a fully developed character, it makes psychological sense to us when an anguished Romeo kills Tybalt for killing Mercutio--especially as Romeo feels responsible for his friend's death. We feel Juliet's nurse's outrage when the high-spirited Mercutio teases her about being a prostitute and Juliet's almost exploding frustration when the nurse takes seemingly forever to tell her about the marriage plans. 

Although the plot is implausible: love at first sight leads to a secret marriage not a day later, a few hours later Romeo is banished, and Juliet takes a potion that mimics death, the rich language and imagery pull us in. The language is so compelling that much of it has almost become cliche: " a rose by any other name would smell as sweet," for example, sticks with us because it describes so well how labels can't disguise reality. We feel Juliet's passion for Romeo because of her language:

Give me my Romeo; and, when he shall die,
Take him and cut him out in little stars,
And he will make the face of heaven so fine
That all the world will be in love with night (III, ii)

Likewise, the imagery Juliet uses when she learns her beloved Romeo has killed her beloved cousin Tybalt conveys her anguish and ambivalence, communicating the fact that life is not black and white, but filled with conflict and contradiction:

O serpent heart, hid with a flowering face!
Did ever dragon keep so fair a cave?
Beautiful tyrant! fiend angelical!
Dove-feather'd raven! wolvish-ravening lamb! (III, ii)

All of these elements together create a piece that sticks with us, gets under our skins and causes us to feel emotions of empathy--and encourages to think about thematic issues the story raises.