Not entirely surprising about its sales in the Arab/Muslim world, given that many of them share AH's views on Jews. Of course, they presumably don't share his views on blue-eyed blond-haired white boys being the rightful rulers of the world, but hey ho.
The restriction needs to be put into historical context, since it dates back to shortly after WW2. The aim of restricting access to this material in Germany was a way for the German state to give some kind of proof to the world that they were turning their back on the Nazizeit and stopping it ever happening again. Like Hirohito renouncing his divinity as emperor of Japan, it was a way to draw a line between the state that initiated WW2 and the Holocaust, and the state that followed the war.
It hasn't stopped racism against immigrants, or the rise of racist groups (in the same way as the BNP in the UK), but Germany isn't unique in having violent bigots amongst its citizens. Since the war is long over, it might be OK now for Germany to withdraw the restriction.
Bonnie, I think the point is to illustrate *why* AH wrote what he did. Remember that without the Treaty of Versailles, this probably wouldn't have happened - the rest of the world got a bad enough recession anyway, but the Treaty of Versailles basically screwed Germany beyond repair. So like the American constitutional right to bear arms, it should be put in the context of why it was originally written. And also it could use the extra interpretation to ensure that phrases can't easily be taken in isolation to serve an agenda. The rest of the world has these annotated versions, the same way we have annotated versions of the Bible, the Koran, the Torah and Das Kapital, all of which are currently being used as justification for bigotry and violence against others (although thankfully Das Kapital is now not such an issue).