AP's obit is here.
Gary had been in bad health for some years, and so this is no surprise; it's a shame, though. He was only 69.
He was always quite nice to me, and I imagine we'll see any number of panegyrics over the next few days. The truth, however, is that Gary's contribution to the field was a mix. He was co-creator of Dungeons & Dragons of course, a landmark game -- but later sought to deny credit (and royalties) to Dave Arneson, his co-designer. In common with many others who become rich over night, he acted, for a time, with an astonishing degree of arrogance; in the 80s, in the pages of Dragon, he seemed to indicate that anyone who chose to play D&D in any fashion other than he, himself, intended, was somehow morally bankrupt (an opinion he later recanted).
He was, of course, later screwed out of his own company, and (also in common with many people who become rich and famous overnight, and then suffer a fall), the experience was chastening. In his later years, he became, in many ways, a far nicer human being.
There is this to be said, though: Throughout his life, from the early days when as a hobby he started a little game convention in his home town of Lake Geneva, and published little miniatures rules sets on the side, to the height of his success at TSR, to the very end of his life, he genuinely loved games. He played them enthusiastically, admired good games from others, and continued designing for his own enjoyment. God knows the industry is filled with people who are driven by ego or personal gain; Gary had his share of both, but at heart, and in a fundamental way, he was as much a game geek as any of us. I'll miss him.