Chained libraries... I'd seen individual books with chains on them before, in museums, but I hadn't realized that there were entire libraries filled with books on chains – and I certainly didn't know that some of those libraries survived to this day. Why were the books chained? Because before the invention of the printing press and moveable type, books were made by hand-copying from the original. It took thousands of hours of tedious skilled work to make a single book, so they were very valuable. It wasn't the calligraphy that was the rare (and expensive) skill back then: it was the ability to read and write – not that many people could!