A smell or odour is caused by volatile compounds which we perceive by the sense of olfaction. An odour of a book is a complex mixture of odorous volatiles, emitted from different materials from which books are made. Due to the different materials used to make books throughout history, there is no one characteristic odour of old books. A professional perfumer has evaluated seventy odorous volatiles emitted from books and described their smells as dusty, musty, mouldy, paper-like or dry.
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.