Don't pretend that you don't do it, or at least haven't done it at one time or another in your life. This is a safe place, and you can be honest here. All book lovers have at one point in their reading life, been known to sniff the book that they were holding in their hands. You may have guiltily looked around first to make sure that you were alone, before tentatively bringing the book that you are holding in your hands up to your face and taking one very quick sniff before you just as quickly withdraw it again. You then glance around to make sure that no one just witnessed that embarrassing episode. Or you may be like me. Openly a book sniffer. I have a addiction to the smell of books.
New books, and old books have very different smells too. Everyone's familiar with the smell of old books, the weirdly intoxicating scent that haunts second-hand bookstores. Similarly, who doesn't enjoy riffling through the pages of a newly purchased book and breathing in the crisp aroma of new paper and freshly printed ink?
A new book smells of fresh paper, ink, glue, and possibly leather depending on what material the book is bound in. It may not sound like a very tantalizing smell, but I dare you to smell one and tell me otherwise.
A old book has these smells as well, but age has changed them. One description is described as "A combination of grassy notes with a tang of acids and a hint of vanilla over a underlying mustiness". Generally, it is the chemical breakdown of compounds within the paper that develops that 'old book smell'. There is a reason for the hint of vanilla too. Older books contain lignin in the paper. Lignin is closely related to vanillin. As it breaks down, the lignin grants old books that faint vanilla scent.
All second-hand books must pass the sniff test before being purchased by me. Some older books were improperly stored by previous owners. Left in boxes in a garage or a attic. These books may have been exposed to moisture, and now have noticeable damage such as mold. Sometimes the only way to tell is the smell. A overly strong mustiness is not appealing to me, I will bypass on these books based on the smell alone. Other books have a overwhelming smell of smoke. I won't buy these books either. I find that the smell will not abate given time, and can also transfer to books that it is touching. Did I ever mention before now that I am a book snob? Because I am. They must not only pass the test of appearance, but also the sniff test, before being added to my collection of literature.
And yes, I randomly will smell a book that I am reading.