This is a Japanese-language illustration (art) book.
Moomins look a little like hippoes, but they're much cuter. This is a hard-cover illustration book containing watercolor paintings of the 'Moomin Valley' world, as well as designs of characters other than the Moomins. Illustrations are captioned in English as well as Japanese. Some text at the back (a couple of pages), all in Japanese, but this will not interfere with enjoyment of the lovely art.