'the only other dangerous books are the books on demomancy, but master sealed those away, he said no one should ever use that magic as it weakens the barrier between this world and that of the demons, but master wouldn't destroy them as he doesn't want any knowledge to ever go lost' number 3 said slowly and clearly, he then scuttered off again and came back with a book titled library content, the book seemed very large, it was filled with hundreds of categories each with many sub-categories ranging from basic of life to categories as specialised as spoon based magic, he even had books about children stories and fables, some of which were but in a category of "stories of interest". Each category also listed every book in it.
the study of demons is called demonology and is perfectly legal, demomancy is spells channelling the powers of demons, the only legal use of it is to open a passage way to the demons world under highly supervised conditions. This is very common knowledge for all nations. The existence and power of demons is also very well known about, they can easily skin a person in a blink of an eye and then keep them alive for how ever long it entertains them, though no demon is known to ever leave its world. Killing or capturing a demomancer with proof is highly paid in any country(only capturing is paid in ethsich though killing them would only be considered a minor crime)