Disch was part of science fiction's New Wave back in the 60s. Along with folks like Michael Moorcock, Philip K. Dick, Roger Zelazny, and Philip Jose Farmer, he tried to close the gap between tradional sci-fi and mainstream fiction and inject it with the spirit of radicalism that was rampant at the time.
My first exposure to him was The Dreams Our Stuff Is Made Of, a collection of his essays about science fiction, which played a big part in getting me back into the genre after studiously avoiding it for much of my twenties. After that I read his amazing novel On Wings of Song, which is one of my favorites to this day (and one which is probably overdue for a re-read). Camp Concentration and The Genocides followed.
Like Edgar Allan Poe, I think Disch would have preferred that people remember him for his poetry more than his prose, but I can't grant him that mercy. I just liked his sardonic, challenging, political, ironic, and cynical fiction far too much.
Disch lost his longtime companion Charles Naylor a couple years ago. For much of that time, I've been reading his blog (tomsdisch), a curmudgeonly collection of rantings (much of it against Bush and the landlord trying to kick him out of his rent-controlled apartment), poetry, and occasional self-promotion. It was an interesting, though sometimes troubling window into his mind.