My tastes in fiction tend to be rather old-fashioned, for lack of a better word, and I never was able to get past the opening pages of Infinite Jest, David Wallace's huge 1996 novel and magnum opus. But you needn't have been a fan of his work to find his recent death, at age 46, very sad.
The long NYT obituary, published Sept.14, gives some indication of his talents and accomplishments. For instance, he graduated summa cum laude from Amherst in 1985, with two senior theses: one became his first novel The Broom of the System, the other was on Aristotle. He was a "prominent" the obit says -- which I assume means nationally ranked -- junior tennis player, and tennis figures in his writing. He also received a MacArthur genius grant.
In addition to the obituary and an appreciation in the NYT, there's also a post at the blog Paper Cuts, which quotes a good passage from Infinite Jest.
Added 10/16/08: For a longer post on Wallace with more links, see here.