[duncanfwalker]

There's a few different things in there that I think have different answers. I'd draw a distinction between banning and curating to cover the quality points.

I don't know what it's like in other parts of the world but I'd say in the UK there's a clear consensus that people shouldn't be able to incite violence - and that covers books.

Suicide and self-harm is a bit more tricky, there are books that deal with those topics that might be important to include in a curation depending on the context - e.g. the readers age and how vulnerable they are.