I'm a huge fan of the Moomins I have all the books. I'd say they are quite dark as children's books go. When I was a kid, dad build me a large Moomin valley out of wood and papier-mâché, about 3 foot long. He also made me a Moomin house and made all the Moomins out of clay and painted them <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> Tove has also written books for adults as well. I particularly like Summer Story, you can see where she got a lot of ideas for the Moomins from when you read that.
