Written in ottava rima (eight lines of iambic pentameter with an abababcc rhyme scheme), Don Juan consists of a dedication, 16 full cantos (averaging around 100 stanzas) and the introductory fragment of a seventeenth canto. Byron reported that he planned to write many more, boasting that these were but an introduction; his death in Greece at 36 years old marked the end of the poem. If the nominal hero of the poem is Don Juan, the protagonist figures far less than the narrator himself. Because the bulk of Don Juan is an extended riff on other poets, history, patriotism, philosophy, religion, glory in war and social mores, it is not inconceivable that Byron could have gone on for far longer, in the superficially desultory, conversational tone of the narrator.

Don Juan, though beloved and loving, is not a rakish libertine, but a rather sweet young man without much personality. He can be heroic at times, and so worthy of an epic, and yet is often quite passive, especially with the richly-evoked women who dominate the story. His survival is not so much due to his naïveté as to a wholesome innocence, and his loves are marked by fidelity as well as amorous passion.

Byron's famous comedy glitters with caustic couplets and is a paragon of the satirist's art, slashing at cant, hypocrisy and the elevation of mediocrities (or of those whom Byron sees as mediocrities). Byron squeezes humor out the poem's overall form, celebrating "unity" in a poem whose most consistent unity is its digressions, all the while apologizing for the digressions that make up much of the book. He exploits to comic effect the ottava rima itself, with its rhythmic crescendo leading to the concise bathos of the final couplet. Similarly, he has a great deal of fun with the art of rhyming, always finding the most damning homonym.

But while Byron produces comedy out of cannibalism, shipwrecks, religious figures, catastrophes, martial and political heroes, and family relationships (particularly between husband and wife), there are moments of tender compassion and affecting gravity (the death of Haidée in Canto IV is one such moment; the battle of Ismail in Canto VIII is gut-wrenching).

Health care workers may particularly enjoy Canto X where, in the Court at St Petersburg, Juan becomes ill, "at which the whole court was extremely troubled / The Sovereign shocked, and all his medicines doubled" (X.39). The narrator reports the court's speculation about the cause in Stanza 40 and, in Stanza 41, provides a list of prescriptions and medical interventions. Stanza 42 is a charming commentary on how people think of physicians (" . . . But although we sneer / In health, when ill we call them to attend us / Without the least propensity to jeer.")