Get The Divine Comedy straight once, then move.

The Divine Comedy begins with Dante the pilgrim waking up lost in a dark forest at the midpoint of his life. He tries to climb a sunlit hill but is blocked by three beasts representing different sins. Virgil, the great Roman poet, appears and tells Dante the only way forward is to travel through the realms of the dead. Beatrice, the woman Dante loved and who died young, has sent Virgil from Heaven to guide him.

In Inferno, Dante and Virgil descend through nine concentric circles of Hell. Each circle punishes a category of sin, and the punishment fits the offense in an ironic, often brutal way. The lustful are swept around in a storm forever. The gluttonous wallow in filth. The wrathful fight each other in a swamp. As they go deeper, the sins become worse: heresy, violence, fraud, and finally treachery. Dante meets historical figures, mythological characters, and his own Florentine contemporaries at every level. Some he pities; some he condemns without mercy. At the bottom of Hell, Satan is frozen up to his chest in ice, beating his six wings uselessly, and his three mouths chew on Judas, Brutus, and Cassius for eternity.

Dante and Virgil climb out through the center of the earth and emerge at the base of Mount Purgatory, an island in the southern hemisphere. Purgatorio has a different atmosphere entirely. The souls here are saved; they're just not ready for Heaven yet. They suffer willingly because their suffering has a purpose and an end. The mountain has an antechamber and seven terraces, one for each deadly sin. As Dante climbs, an angel erases one of seven P's (for peccatum, sin) from his forehead at each terrace, marking his own moral progress.

In Purgatorio, Dante encounters his old friend Casella, who sings one of Dante's own poems. He meets the poet Statius, who joins them for the rest of the climb. He also passes through a wall of fire near the top, a moment of real fear for him, before entering the Earthly Paradise at the summit. There, Beatrice appears and Virgil quietly disappears. Beatrice is not gentle with Dante. She confronts him directly about his moral failures after her death, and he weeps with shame before she forgives him.

Paradiso takes Dante and Beatrice upward through nine celestial spheres, each associated with a different virtue. Souls appear in each sphere not because they're stuck there but to show Dante a comprehensible version of their glory. He meets crusaders, theologians, his great-great-grandfather Cacciaguida, and the apostles. As they rise, the light intensifies and language starts to fail Dante. He repeatedly warns the reader that what he saw cannot be fully described.

The poem ends in the Empyrean, the realm beyond space and time. Beatrice takes her place among the blessed, and the mystic Saint Bernard of Clairvaux guides Dante for the final stretch. The Virgin Mary intercedes so Dante can look directly at God. For a single moment, Dante sees the entire universe held together in one point of light, and he glimpses the mystery of the Trinity and the Incarnation. Then the vision ends. The poem closes with Dante's will and desire turning in harmony with the love that moves the sun and all the stars.