Whether the older books on your shelves consist of rare first editions or tomes that are only valuable on a sentimental level, they need a certain level of care. Maintaining your older (pr pricey, or pretty) books will help them retain their monetary value, if applicable, or just ensure that they will be readable for years to come. Here are a few must-dos, collected from experts around the web:
Store old books (or any book you want to pay extra attention to) out of direct sunlight. If your shelves are in sunlight and there’s nothing you can do about it, wrap the dust jacket in a UV-resistant plastic book cover (available at craft stores or online). Sun will permanently fade dust jackets and covers, which can severely devalue rare books.
Keep the books away from heat sources like the air vents. Dry heat can crack leather spines and make book glue brittle. Also, keep them away from potential water sources like A/C units, pipes, and leaky old windows. The condensation from these water sources can lead to mold growth on the paper. According to the National Library of Scotland, the ideal temperature for book storage is 60 to 66 degrees F, and the ideal humidity is 45% to 60%.
Be sure you don’t shove your old books in too tightly on the shelves. The pressure isn’t good for the spines and you might damage them when you try to pull them out. For older folio-sized books and books that are 3 inches or wider, store them flat (and in stacks of no more than three). For other books, store them upright in a shelf with books that are about the same size- this will prevent warping. Don’t leave books stacked in piles, or open and face-down. And speaking of pulling books off the shelves- don’t pull on them by the top of the spine. Reach back and pull them out by the pages while the book is closed, or pull them out with your fingers on either side of the spine. If you are storing the books in wooden shelves, make sure the shelves have been sealed so acids from the wood don’t leach into the paper.
If your books are so rare/valuable/kick ass that you’re worried that they might be stolen (or that a friend will borrow them and not return them), write your name or whatever mark of ownership you desire on the back of the title page in pencil. According to the United States National Park Service, in the case of theft and erasure of the mark, the police will be able to detect the erased markings with their fancy-shmancy cop technology.