Thomas, Uttlesford asked:
What is the smell of old books? The older the book, the better it smells. I’m not talking about the old mouldy smell of an ill-kept book. I’m talking about the heart-warming smell of a book you’ve loved and kept for twenty years. What is the smell of old books?
We put this question to Jana, Head of Laboratory for Cultural Heritage at the University Library of Slovenia.
The pleasant aromatic smell is due to aromatic compounds emitted mainly from papers made from ground wood which are characterised by their yellowish-brown colour. They emit vanilla-like, sweetly fragrant vanillin, aromatic anisol and benzaldehyde, with fruity almond-like odor. On the other hand, terpene compounds, deriving from rosin, which is used to make paper more impermeable to inks, contribute to the camphorous, oily and woody smell of books. A mushroom odour is caused by some other, intensely fragrant aliphatic alcohols.
A typical odour of ‘old book’ is thus determined mixture of fragrant volatiles and is not dominated by any single compound. Not all books smell the same.
This is just speculation, but it's probably due to some combination of oxidation (which is the process that turns old paper yellow) and contamination with microorganisms such as mildew. Even books kept dry and contaminant free will probably pick up enough moisture and spores from the air to get a bit of mildewing. jpetruccelli, Wed, 13th Feb 2008
I think John (bored chemist) is away at the moment. Here is an answer he previously gave to the same question. Hope he does not mind me quoting it here?