This Moomin picture book is written and illustrated by Tove Jansson, a Finnish novelist, painter, honorary Professor of Philosophy, illustrator, and comic strip author. She wrote and illustrated her first Moomin book (The Moomins and the Great Flood) in 1945, during World War II. She said later that the war had depressed her, and she had wanted to write something naïve and innocent.
This book is from 1977. I bought it at a thriftshop