This recollection of "At Home with the Marquis de Sade" (see references below) is largely drawn on memory, I do not have my copy handy to check every detail. I will claim that it is accurate in tenor if not every detail.

Recent biographies de Sade largely replace the myth and rumor which has surrounded the use of his name as the foundation of the term 'sadism'. The Marquis, seen with rigor of historical study comes across at least partly in character with his time, and also having some distinctly different views than either his fellow libertines or indeed any element of pre or post revolutionary France.

Unlike his contemporaries de Sade allowed some of his exploits to become quite public knowledge. He also was unique in writing extensively about his views on atheism and Certainly many of his aristocratic contemporaries engaged in more serious debauches, however most were more politic about them. De Sade managed to curry the favor (or escape the notice) of most of these regimes at one time or another. The Marquis was very nearly executed during the Terror following the revolution, being at the time imprisoned in the Bastille, he was witness to many executions. This experience clearly had a profound effect on his later views and writings.

Equally, however, in the wavering mores of the times made he still managed to be the target of one or another element of every government from the House of Bourbon to after the rule of Bonaparte. At several junctures his fortunes hinged entirely upon the support of his wife's powerful and wealthy family. That was later to be his undoing when they decided it was prudent to see that he stayed incarcerated.

Sexual life

De Sade had a strong appetite for sex, and inevitably when that was restricted to 'vanilla' sex (even if relatively frequent), he would eventually arrange a debauch, characteristically of epic proportion. And inevitably he was caught after most of these.

There was one extended period, less well documented when he lived in relative peace and indulge his pleasures for several years at his family's estate at La Coste in Provence. After that extended stay he spent most of his years in prison.

SM life

De Sade went to great effort to arrange various debauches, usually with close friends and usually the entertainment was paid prostitutes. This was quite similar to the approach of his contemporaries, except that de Sade was actually more private and held smaller 'events' and being perceived as secretive (with respect to themselves) caused his peers to think of him as a pervert.

De Sade's often immature approach to life led him (again like many of his contemporaries) to substantially out spend his income. By today's standards many would view him as a perpetual spoiled adolescent.

The prostitutes of the day included famous, sought-after and expensive women and de Sade used some substantial part of his resources trying to maintain women of this calibre. However usually for his debauches he would seek out less expensive women, who generally were not in agreement with what he had in mind.

And inevitably when these parties were over these women would talk to their protectors or the police and de Sade would become the focus of another scandal. Some of the women were paid off (by de Sade's in-laws), but as time went on each new arrest resulted in a heavier sentence.

Most of the Marquis's writings were composed while in prison. Especially in the later years of the Napoleonic empire, they were traded only illegally and it seems that de Sade repudiated his authorship of many of them in order to escape further prosecutions. The various scandalous pornographies varied from extraordinarily long and detailed revues of (almost entirely) imaginary scenarios (which differs from the SM and pornography of today foremost in its highly repetitive verbosity)..

De Sade (like most of his peers) engaged in homo-erotic as well as hetero sexuality. He also was not purely a sadist, as it is well documented that he enjoyed playing on either end of the whip.

As other wu's have suggested it is not possible to make the Marquis de Sade into a modern practioner of leathersex. However this is a facile truism. The terms Sadist and Masochist did not then exist, and he lived a century before time when psychoanalysis would 'define' homosexuality and the wide array of paraphilias of which sadomasochism is only one example.

De Sade's story is more complex than his simple notoriety would suggest. He was unique in his time for having expressed strong (and original) views about the nature of sexuality, morality and religion.

Above all the hype the Marquis de Sade had great influence on the later course of modernism and surrealism. While his writings can be repetitious to the point of exasperation, they remain unique and influential today.

References:
http://dir.salon.com/sex/feature/2000/12/07/sade/index.html

is written by the author of:
Francine du Plessix Gray At Home with the Marquis de Sade