http://myanimelist.net/forum/?topicid=584245
The link has an official statement from Media Factory in Japanese, if someone wouldn't mind translating.
He died at 41 of cancer. If the comments are to be believed, he was close to finishing the volumes of the show. Another poster had this quote from him on twitter in 2011:
"Novel author Yamaguchi Noboru posted in his twitter that he will be hospitalized tomorrow and will take a major surgery in August. He said he would have been dead if he had missed the chance to take the operation. "The 21st volume of Zero no Tsukaima novel will be delayed at least for two months. Please forgive me! Damn! I'll live on. I had been desperate, but I miraculously got an opportunity to take the operation. There is a possibility of survival. I really want to live.""
If you've never seen it, it's a pretty popular anime as well, I enjoyed it a lot. One of the main characters are voiced by Rie Kugimiya, famous for her tsundere roles, such as Aisaka Taiga and Shana, as well as Louise in this show. Just thought this was worth posting for anime fans, he was a bit too young for this.
