There are only three banned porn varieties I know of (depending on jurisdiction), which are child porn, bestiality porn, and nonconsensual/revenge porn.
And calling those things "books" is just nonsense. You know what we are talking about when we say "books", and it isn't that.
The Convention for the Suppression of the Circulation of and Traffic in Obscene Publications, which is ratified by most countries, and only denounced by Denmark, Germany, and The Netherlands, bans most porn.
And calling those things "books" is just nonsense. You know what we are talking about when we say "books", and it isn't that.