How do I get mildew, must, and mold smell out of books?

Place the books in a cardboard box with activated charcoal for about a week. You might also place a moisture absorber like the DampRid tub in with the books and charcoal. The DampRid crystals will absorb any moisure out of the book (if there still is any) to prohibit future mold and mildew growth and the activated charcoal absorbs odors.