Strong light is a major enemy of books, it fades covers and makes paper go yellow.
Light, particularly the ultra-violet rays, causes chemical reactions that cause paper to become dark and brittle. Always store books away or shaded from strong natural light and use low UV interior lighting. They allow heaters to stand next to collection material. Heat speeds up the natural chemical reactions that occur as materials age. So extra exposure to heat will make paper and books old, fragile and useless before their time.