The Rainbow Goblins has been a favorite of mine since I first discovered it not long after U.S. publication in 1978. His family's announcement of his death notes that it came after years of suffering endured with admirable bravery. Perhaps that explains why The White Goblin (1996) was his last book.
His passing seems to have had no notice in English-language publications. Some of his art can be seen here. Note the short biography at the very bottom of that webpage.