By far the most interesting banned books are those about ideas. These never appear on banned books lists because they have been censored so successfully (usually > a hundred years ago) that journalists and researchers don't know about them and no english translations exist (indeed it is often those translations which are the banned versions). Most of them are in Russian or German, some Romanian or Hungarian.
curious, do you have a example or two of these? would love to read more about them
Here's an example: Gekaufte Journalisten (Bought Journalists)
This author: https://en.wikipedia.org/wiki/Udo_Ulfkotte ?
With books available via amazon and reviewed on Good Reads? Material can be unpopular and not sell well for many reasons other than state conspiracy to suppress.
It must be that ideas are powerful, maybe the most powerful things. Ideas can move nations, start wars, create revolutions. They can create widespread hate and widespread compassion.
It's as if we, the public, aren't as helpless as we thought, but that mass manipulation via social media - manipulation of ideas - could be exceptionally powerful.