From video’s description on YouTube:
Walk into a used bookshop and you will encounter the unique aroma of aging books. The smell is loved by some, disliked by others, but where does it come from?
A physical book is full of organic material that reacts with heat, light, moisture and – mostly importantly – the chemicals used in its production. The smell comes from the reaction of the organic material to these factors.
Books printed by the earliest printers have survived for 500 years because the purity of their paper.
Telltale signs of this deterioration is browning – an all over discoloration of the pages – and foxing which are localized brown spots.
Books can also react to external materials. A newspaper clipping stored inside a book can cause a reaction through its ink and cheap acidic paper.
Books can absorb strong smells from the environment and this is commonly seen with tobacco smoke. The best way to store your books is in a cool, dry environment away from direct sunlight.
Learn more about book care at the AbeBooks’ Book Collecting Guide:http://bit.ly/ujYGTh
Jane Austen Society of North America - New Jersey Region 
I absolutely love the smell of old books. It's good to know where the smell is coming from. Thank you for sharing 🙂
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You're welcome. I learned about the smell of old books when I took an archiving class in graduate school and just it was so fascinating. So much of what we love about old books is really harmful to them.
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