When you ask your literary friends why they like physical books more than e-books — if they don’t immediately roll their eyes at the question, that is — they might tell you it’s because they love the smell of books. Well, we agree that there’s nothing quite like the aroma of a used bookstore or a worn paperback, but we’ve never stopped to think about exactly what gives our dusty tomes their scent. Until we watched this very informative video from Abe Books, that is. “A physical book is made up of organic matter that reacts with heat, light, moisture, and most importantly of all, the chemicals used in its production,” we are told. “And it is this unique reaction that causes the unique used books smell… Old books release hundreds of volatile organic compounds into the air from the paper,” and it is this which gives books their scent, “a combination of grassy notes with a tang of acids and a hint of vanilla over an underlying mustiness.” Mmm. Click through to watch the video, and then you can get right back to happily sniffing your bookshelves.