Written by Dante Alighieri in 1306 - 21. The time setting when the book begins is in 1300, so he uses his knowledge of the present to "predict" events.
It is divided into 3 sections: Inferno, Purgatorio, and Paradiso. Each one of these sections is divided into 33 cantos (except Inferno, which has 34 cantos), which are written in tercets (groups of 3 lines). The number 3 in Dante's time was significant because it was considered holy--since the Father (God), Son (Jesus), and Holy Ghost comprise the Trinity.
Dante Pilgrim and Dante Poet shall henceforth refer to Dante as the main character in the Comedia and the author, respectively.
quick summary:
Dante Pilgrim has not been a good boy. His dead love Beatrice asks the Virgin Mary to help him see the error of his ways. Mary accepts and Dante is sent on a three-day trip through Hell, and on up Mount Purgatory on the other side of the world, and finally to Heaven in the sky.
He is spiritually lost at the beginning of
the story, so he needs guides to help him along the path.
His first guide, through Hell and Purgatory is
Virgil (author of the Aeneid). They encounter
many interesting sinners on the way. Dante
learns to hate sin.
His second guide is Beatrice, the woman he
adored while she lived. His final guide is
Saint Bernard (namesake of the loyal dog), who
takes him to see God.