Mold and mildew forms on paper, including books and wallpaper, when they are exposed to damp conditions for several months or years. This mildew formation is called "foxing." The term refers to ferrous oxide, or iron, that becomes attracted to paper and leads to the unwanted discoloration. Removing foxing from paper, both in books and wallpaper, is possible, and doing so can restore the original appearance without causing further damage.
Inspect the book for any remaining moisture. If the books is only slightly damp, open it up in the center and set it in a dry, warm area.
Sprinkle corn starch onto any pages that are very wet. Allow the corn starch to remain for 10 to 15 minutes before wiping it away with a soft cloth. Then lay the book out in the manner described in Step 1.
Allow the book to remain laid out until it is completely dried out. Once this has occurred, wipe away the dry mildew with a soft cloth. Point the book away from you and brush the mildew away toward a garbage can or the ground outdoors.
Dry out the damp wallpaper by increasing the heat in the room. If it is summer, turn up the air conditioner for a few hours, or until the wallpaper is completely dry.
Prepare a mixture of 2 tbsp. liquid dish soap and 1/2 gallon warm water. Wet a soft cloth in the mixture and wring it out until the cloth is slightly damp, not soaking wet.
Wipe down the dry wallpaper with the soapy water. Do not allow the walls to become overly damp.
Wipe down the walls with a separate soft cloth that has been dampened with plain water. This will remove any remaining soap from the wall.
Turn up the heat or air conditioner in the room to dry out the wallpaper. Do not allow the wallpaper to air dry as this will lead to further foxing.