"People who comprehend a thing to its very depths rarely stay faithful to it forever. For they have brought its depths into the light of day: and in the depths there is always much that is unpleasant to see." - Nietzsche (Human, All Too Human 489)
The Marquis de Sade is one of those writers who is often misunderstood - and too easily dismissed. His themes are blasphemy, destruction, and perversity. His ability to offend and horrify are unparalleled. Any attempt at goodness by any of his characters is quickly (or painfully slowly) annihilated.
So with that as a start, why do his books always make these "List of Important Books" lists? Why do thinkers (Camus, Foucault, Lacan, Klossowski) think he is a "writer to be dealt with?" If one can get past the horror-show, is there something more being said? Or, what is really being said here?
To sum up in a short statement his themes: "Nature gives us desires, when we act on them we fulfill Natures purpose, therefore any denial is a crime against Nature." For Sade, the desire is always sexual, the act is always perverse, and the outcome is always, well, you get the idea.
What happens when we carry an idea to it's logical conclusion? What is the nature of desire?
"But," you say, "enough of this bibble-babble, we're reading a book! What about the characters? What about the story? What about the Style?"
Perhaps the most interesting aspect I find about Sade is that as uncomfortable as the stories are, he is a writer of consummate skill. Never has a writer amassed such a cast of characters. His creativity is prolific, pure, relentless, and bewildering. For artistic beauty and Style he rightfully owns his unique place in literature.
A comment on his themes:
The ideas in the stories are, as Lacan calls them, fantasms - they are not meant to be taken literally as ideas to be implemented in society. That would be just plain silly.
If you are not familiar with Sade I would suggest a taste before you buy. If you try a little bit and are not liking it, stop - it only gets worse. But, if you are up for a horror-show, it's a ride unlike any other.