There are dozens of flavors of old book, but the one that leaps to mind is the mixture of musty, dust and the aftereffects of moisture, combined with the decomposition of paper and ink, and depending on the vintage, a bit of skin-warmed leather.
The first thing I do when I pick up an old book from a shelf or a pile is to open it, dip my nose in, and inhale deeply. Only after this is accomplished to I back off and actually read the words on the page. It’s probably not a surprise to learn that there are books that I’ve purchased or brought home only because of that first breath of their history. In addition to evoking images of a more restful past, I also feel hopeful when I catch this smell – I have to believe that books will always be with us.
I once saw a Tufte lecture where, in the middle of the day, he walked his first edition, 400-year-old copy of Newton’s Principia Mathematica, around the room. It killed me not to have been allowed to smell it, and for better or worse, that’s what I remember most about that day.