The presence of cellulose in book pages is not necessarily a sign of mold. However, if the books do smell musty, it is possible that mold is also present. Mold is a type of fungus that can grow on paper and other materials. It can cause the paper to become discoloured and brittle, and it can also produce a musty smell.
If you are concerned that the white powder in your book pages is mold, you can clean it off with a soft brush or a vacuum cleaner. Be sure to wear gloves to protect your hands. You can also try wiping the pages with a damp cloth. If the powder does not come off easily, you may need to use a mild detergent. Be sure to test the detergent on a small area of the book before using it on the entire book.
Once you have cleaned the book pages, you should air them out in a dry place. This will help to prevent the growth of mold. You can also store the books in a cool, dry place to help prevent future damage.
The white powder in book pages is generally not harmful, and it can be cleaned off and the books can be safely used. However, if you are concerned that the powder is mold, you should take steps to clean it off and prevent the growth of mold.