It isn't a novel per se. I've read parts of Inferno.
The Divine Comedy consists of three parts: Inferno, Purgatorio and Paradiso.
Dante is lost in the woods and basically ends up in Hell. Beatrice, as mentioned, is in the story yes, based on a woman he loved when he was young. He is guided through Hell by Virgil through the nine circles of Hell. Among these circles are the Seven Sins explained (Pride, Lust, Greed, Gluttony, Sloth, Wrath, Envy). In the third circle, Dante encounters Cerberus (note that in Devil May Cry 3, Cerberus is encountered on Mission 3). After passing Inferno, Virgil must leave Dante in the hands of Beatrice to guide him through Purgatory since he can't continue on himself.
It's an epic. It means that basically, long series of poems (and cantos) written to tell the story. It's hard to read. It's very good, nicely written, but hard to read.