Did pippi longstockings start off as a book?

Good question. The thing is that the story of Pippi Longstocking occurs in a "real world" or a world very similar to ours. But, she has some uncommon abilities that sets Pippi apart from the category of "a normal child". She doesn't have magic, but the story is fantastical for the things she does. It could be classified as "low fantasy" or "magical realism". You may have a look at the low fantasy page on Wikipedia to enhance the term and its usage. See the related link below.