I like the theory that the book could’ve been written by Blue. Would be a literal translation of the term “fairytale.” Maybe I’ve been watching too many Christmas movies, but I like the idea that the fairies collectively wrote the book together- like they were trying to hurriedly record a personal history before the curse was cast. Like some sort of map or key for the savior.
I can still remember Blue’s words from the premiere episode. She leaves Snow and Charming (I think) so she and the fairies can “make their final preparations” before the curse is upon them. I would like to believe that this line was purposely included as part of the plot and not just a bit of filler.