This is sad news.
I met him when he came to my school to discuss his books. I was 10 at the time, and generally only interested in reading Goosebumps, Fear Street, etc. After meeting him & listening to him read some pages from Mattimeo I decided to give one of his books a try. Since then he's always been one of my favorite authors. Even now, as an adult, I still enjoy reading the Redwall series. He was a wonderful writer and storyteller.