It seems he has been ill for a while, and so the sadness is mitigated by the thought he no longer suffers.
I'll share a personal memory:
I discovered him during my military service, ten years ago. I had found a little book of his in the base's dilapidated library, The Long March. It's a powerful novella that had me spellbound. I later learned he wrote Sophie's Choice, and watched the movie, which featured fantastic acting from Meryl Streep and Kevin Klein.
Then, some time later, I was on a US visit (on behalf of my employer), and found Darkness Visible, his memoir of depression, and bought it just because it's by Styron. Bizarrely, that same evening, in my hotel room, I was suddenly seized by a terrible depression, the like of which I had never before experienced. Everything lost its value, all humanity seemed to fade into distant memories of something whose point you once knew but can no longer recall, and any action or word seemed futile.
To this day I have no idea what triggered that bout of depression. While trying to figure out what's happening to me, I noticed Darkness Visible book in the big, full bag of books I had purchased at B&N earlier that day, and instinctively reached for it. I read most of it that night, with an eerie sensation that I must find some solution in it. The book offered no solution, but I was nevertheless much relieved and calmed by reading it. The depression lasted three whole days.
At the time, life was hard to bear, and I did think of suicide. But in retrospect, I'm actually glad I have had that experience, especially since it was quite short, because it made me a lot more understanding of the phenomenon of depression in general, and of people close to me who have had episodes of severe, clinical depression.
All this has little to do with Styron, I realize, but to me his name is always associated with that book and that episode.