Unlike the epic poems of Homer and Virgil, which told the great stories of their people's history, Dante's The Divine Comedy is a somewhat autobiographical work, set at the time in which he lived and peopled with contemporary figures. It follow's Dante's own allegorical journey through Hell (Inferno), Purgatory (Purgatorio), and Paradise (Paradiso). Guided at first by the character of Virgil, and later by his beloved Beatrice, Dante wrote of his own path to salvation, offering philosophical and moral judgments along the way.
Dante is credited with inventing terza rima, composed of tercets woven into a linked rhyme scheme, and chose to end each canto of the The Divine Comedy with a single line that completes the rhyme scheme with the end-word of the second line of the preceding tercet. The tripartite stanza likely symbolizes the Holy Trinity, and early enthusiasts of terza rima, including Italian poets Boccaccio and Petrarch, were particularly interested in the unifying effects of the form.
Also unlike the epic works that came before, The Divine Comedy was written in the vernacular Italian, instead of the more acceptable Latin or Greek. This allowed the work to be published to a much broader audience, contributing substantially to world literacy. Due to the monumental influence the work has had on countless artists, Dante is considered among the greatest writers to have lived. As the poet T. S. Eliot wrote, "Dante and Shakespeare divide the world between them, there is no third."
http://www.poets.org/poet.php/prmPID/1664