By definition, vegans do not use any animal product, food or otherwise
Veganism is a way of living which seeks to exclude, as far as is
possible and practicable, all forms of exploitation of, and cruelty
to, animals for food, clothing or any other purpose.
Although I know many Vegans, I do ...
In the UK, cheeses made with non-animal rennet (the majority, as you say) are typically labelled in a user-friendly way, including the text:
Suitable for vegetarians
and in the ingredients we can find the phrase
The use of non-vegetarian rennet is usually denoted, in my experience of asking makers and manufacturers, by the absence ...
If it took killing to produce, I wouldn't eat it. That would go against my morality.
However, there is also the bigger picture here. Millions of animals die everyday just for the consumption of their flesh. If one calf being killed is going to stop many more from not being killed, I can understand why a group dedicated to animal welfare would support it.
Only in rare cases will you find a book that contains any animal components. Things you might encounter would be leather and vellum in bindings, and extremely rare gimmic inks.
Vellum is prepared animal skin, it has been used instead of paper and was until recently used to record British laws.
If you buy an old book, it's possible though highly unlikely ...
My father was a bookbinder. In the western world and with mass production, nowadays apart from a leather cover on specialty books or maybe a leather bookmark on premium books, there are no animal products used in book making.
About the only thing where it could be used is the glue holding the cover to the pages and modern techniques use a hot-melt glue ...
The US does not require manufacturers to label such things. So, unless the product specifically states it is vegan or vegetarian, I would presume it contains or uses rennet or other enzymes for all we know.
A simple google search yields a few sites with "safe" lists - What are the Vegetarian Cheese lists? and Are there any Cheeses that do not contain Rennet ...
Seeing as how the only google results for "QIN leather" reference the Nillkin products, one can only assume that QIN is part of the brand name and not an actual material. The material itself seems to be PU leather which as you mentioned, is partially composed of animal hide.