explaining the smell of old books

For those who have big book collections, this Abe Books guy explains why old books smell the way they do. Actually new books have a distinctive smell too.  One of us likes the new book smell, but not old books, the others have no opinions. 

The problems described from the use of high acid content in book paper applies mostly to cheap paper such as 'mechanical' or newsprint grade which we have rarely used.  Most of our books have been printed on high grade coated art paper.