They are not banned. You can buy his books in book stores across the country and probably find his material in libraries as well. They were just removed from that particular book fair in Riyadh. Anybody can look up his material on the internet as well.
The family is not ruling a whole country. Most of the important advisers and people behind the scene/curtain are not from the Al-Saud family and I have no problem with strong rule or a centralized rule. The ordinary Joe in the UK are not part of any real decision making either nor does he have any influence when it really matters.
The most important thing is stability, economic prosperity and improvements on various fields. As well as not messing with people's religion, culture, customs etc. People are satisfied. They have no major reason to protest.
This is why KSA is so different from any other state out there.
Even the House of Saud got into power through majority support of the people. It were popular movements that facilitated their rule.
Patriotism is big in KSA.