"Moominpappa at Sea" is one of my favorte books of all time. All of the moomin books feel important and significant even that the characters are inocuous or even silly. It is easy to understand how many people missed the more adult messages of the books. But, that same style allowed children to enjoy the stories without overwhelming them.
It is a shame that in places like Japan, the characters are very well known, but the books are shadowed by the animated version. The characters are fantastic, thou.
For Pipi, everybody loves the 1969 TV show. I have read a couple of books, and I like them, but I do not have them in such regard as the Moomins books.