The book whose philosophy has held me more than any other is Dante's  Inferno, written around 1310. I read 

it haltingly in Italian, and with speed and joy in English (preferably the Dorothy L. Sayers translation, with captions and fascinating footnotes). There is passion and music in it, wit, character, and imagination 

to equal that of any sci-fi or horror story. And the plot carries you forward at a hectic pace, always wondering what next.

Why do I care? We spend our lives fascinated with mankind, and with the quest to understand good and evil. Dante encapsulates the soul of it in his vision showing how we are not punished for our sins, but by them. It is not an external thing visited upon us by God, or fate. It is an internal change we have wrought in ourselves. Each bad choice diminishes us in a particular way, just as each good one adds to us.

His classification of sins is most thought-provoking. Lightest are the sins of the Leopard - those of incontinence. In the middle are the sins of the Lion - those of violence. Deepest are the Sins of the Wolf - those of fraud, deceit and betrayal - a capacity peculiar to man.

Among these lowest are flatterers (debasing the means of communication between individuals): forgers (destroying the means of trade); propagandists (polluting all trust and belief between peoples). Pollution of the earth we now understand and condemn as damaging the very world we live in, and therefore all life. Who else grasped that in 1300?

For sheer enjoyment - and perhaps a touch of "schadenfreude," there are the grotesque punishments so exquisitely fitting the crimes - e.g., the lustful swept along by violent winds, never allowed to rest; thieves who now cannot possess even their own bodily forms and are forever changing. It gives the term "poetic justice" a whole new meaning.

And there is the beauty. In that terrible place you still see Christ "walking the waters of Styx with unwet feet."

Every time I return to it I am caught up in the power of Dante's imagination and made to think again "Am I turning myself into who I really want to be? If I saw my acts without the comfortable mask of self-delusion, would I still want them to be part of me?"  Thank you, Dante Alighieri.