Good ventilation and UV light should help and if that is not practical try ozone treatment.

Good ventilation and UV light should help and if that is not practical try ozone treatment.

That's the smell I love when I enter a used book store.

Ozone treatment is your friend. Dry cleaning services, and disaster restoration companies use ozone rooms to remove all kinds of odors.

Don't know about the musty smell, but I do know that placing sage leaves with them, dried as you'd use in cooking, will keep silverfish away. All the best making them smell better.

It sounds as if the conditions they are being kept in are slightly too humid - not enough to cause mould but enough to make them musty. Can you dehumidify a bit?

One of the cleanest, simplest, least costly, and safest methods I've used works reasonably well if the situation isn't severe, and the number of books is not too large. Get clean, new newsprint paper (do not use newspapers because of the inks and other chemicals in them from printing). One such supplier is Aviditi. The product is NP203025 100 Percent Recycled Paper Newsprint Sheet, 30" Length x 20" Width, White. A case contains 600 sheets. This stuff is acid and other chemicals free.

Cut several sheets to a size approximately 1/4" larger than the pages of the books to be treated. Slip a sheet between every 10 to 15 pages of the book. Make sure to get a sheet in the inside covers, too. You can do a few books at a time.

Get a clean cardboard box (be sure it is dry) that is a few inches wider and longer than the largest book being treated. Tape the bottom seams. Pour a goodly amount of baking soda in the bottom of the box and spread it around evenly. Place wadded up sheets of paper in the bottom so that the books will not come into direct contact with the baking soda. Carefully center the books in the box and stack them until there is a clear space of an inch or so when the top is closed. Wad up more sheets and place them around the spaces at the edges of the books. Close the top of the box and keep it stored in a dry place for about a week.

When the books are removed from the box, they should be odor free. They get that musty smell from being stored in moist environments. In the future, to avoid the problem, keep your books in a room with a dehumidifier. Not too many folks want to go through all that trouble, but some of us treasure our books -- perhaps a bit too much.

It will take time and patience; a face mask (to avoid breathing all the mold spores) and a bunch or old but clean cloths (old towels best). A spray bottle with just a few tablespoons of bleach, mostly water will work well to not only renew the books, but stop the molds and fungi (my girlfriends called me that...a fun -gi....get it? ) but the labor depends on your love of the books, the time you have, and the value of the books.

A cut onion gets rid of paint smell so I would imagine it would also help book. I would think that the main thing is to make sure they are not too damp nor too dry.

I've done things similar to what @Petter suggested only I used potpourri, essential oils with a diffuser, or an open box of baking soda. The transition goes faster if you can put everything into a sealed container making certain the books don't touch the odour removers.

Placing them in a cupboard, with a bowl of undiluted chlorine bleach, seems to help. Make sure that the cupboard has some ventilation, as otherwise the air will become humid - and change the bleach every day.