In my Fairy Kingdom, my rebellious fairy godmother and heir to the Fairy Kingdom throne, Eileen, wrote several volumes of history as she saw it and she did not portray her royal ancestors in that flattering a light.
Had anyone else written them, they would've been jailed by the Queen and her Council on the grounds they were busy fighting the plotting and schemes of the Witch and anything like alternative history would be used as propaganda by the Witch.
Eileen dismissed that as nonsense and insisted she was just being honest but the fact remains if anyone wants to read her books, they have to go to the Palace Library and leave their contact details. Unsurprisingly this puts people off much to Eileen's annoyance. This is not the major point of my novel The Trouble With Mother but it does flesh out Eileen's own history, shows the attitudes held by her and her cousin, the Queen and sets the scene for the fact that major fallings out between the two are nothing new.
So what books would your world(s) forbid and why? Are any of these restrictions overturned (and if so how and who led the campaign to overturn them)?