He is legend, indeed. A quiet legend, but still a legend. It's mind-boggling to think of the extent of his work and the influence he had on many generations of readers and fellow writers.
When I was a young man in the early 80s, I read an interview with him in Twilight Zone
magazine, in which he talked about The Night Killers
, his third Kolchak script, which went unproduced in favor of the TV series. I wrote him a letter, asking if he had a copy of that script that I could buy, since I was such a huge Kolchak fan (heh-- I was about twenty, so perhaps a bit naive). Of course, he didn't, but he sent me back a very nice letter telling me so and explaining why, which I thought was great of him.
Years later, a hardcover collection of all three of his Kolchak scripts came out, which I bought-- when it came, it was autographed, which I hadn't even expected.
RIP, Mr Matheson. The world would not be the same without you.