Are books by the Marquis de Sade worth reading?

Depends on the book and often which part of the book. Some books, like 'Justine' offer some unique philosophical viewpoints and others, like 'Philosophy in the Bedroom' might be 95% ...errrrmm..'adult material' yet contain a brilliant passage (in this case a staggering refutation of the Teleological Proofs of god). Then again, '120 Days' has no redeeming qualities.

No, except out of historical interest. Unless you're into torture porn and run out Larry S&M fanfic or whatever the kids reading these days. They'd appeal to people who thought Fifty Shades of Grey was a masterpiece. I don't think they're well written or interesting-- if you're looking for tragic masterpieces with sexuality and social commentary, see Thomas Hardy.

He,s interesting .Depends on what You,re into .The Guy was a little fixated with His interests.He was revolutionary for His time but now days if it,s kinky You,re into there,s crazier stuff on the market.