Why would you ban Main Kampf? Have you ever even read it?
Its ultra important for historical/social and linguistic education.
I read it when I was 14, and I'm from Poland.
It is AWFUL and PAINFUL to read due to the horrible styling - which amuses me to this day. :) That's why no need to ban it hehehe
Nowadays books are for intellectuals, not for the masses... That's why I would be ok for any modern teenager to read anything 18+ or anti-whatever books :) It's net positive no matter of content IMO.