Udisha
Keep them out of direct sunlight
If your books are turning yellow, it is due to oxidation. To prevent this, shield your books from direct sunlight because the UV rays speeds up oxidation.
Control the temperature and humidity
Too much heat, humidity and moisture can lead to yellowing and cause mold on the books. To avoid this, store books in a room that is dry and cool and does not get humid easily.
Ensure good air circulation
Books also need air to stay healthy. When you are storing them, make sure there is enough space between them for air to circulate. If they are tightly stored, moisture can get easily trapped, causing them to turn yellow.
Handle them with clean hands
Be very careful when you are handling books. If you are touching books with dirty, oily or sweaty hands, the grease will transfer onto the page and cause yellow spots. Always make sure your hands are clean and dry. While it is not possible to completely prevent oxidation especially for old books, but you can certainly delay it.