There are many steps one should take to prevent damage and aging to collectible books. Proper care can be simple, and can prolong a book’s fine condition almost indefinitely.
Environment: The ideal manner in which to store books is in a dry and cool room. Heat will accelerate the natural deterioration of a book, so it is important to not place shelves anywhere near a radiator or heating duct. Personally, I have disconnected the heating units in my library, and not only does it act to help preserve my books, I save considerable money on my home heating costs.
Sun is also a major threat to your books. Direct sunlight fades leather, cloth, or paper, which is bad news for books. A faded spine on a book or its dust jacket can negatively impact its value – making an otherwise fine volume near worthless.
Humidity not only causes rot, but it invites insects, and can cause mold. Books should never be stored in basements, attics, or garages.
Treatment: How you handle a book when you read it can impact condition quite easily. Dog-earing pages, forcing a binding open to the point where it cracks, and laying a book flat on a surface are sure fire ways to turn a collectible book into a table coaster. Both covers should always be supported while reading. It should go without saying that underlining, highlighting, and paper clips inserted in books will negatively impact their value.
It is highly advisable to remove a book’s dust jacket prior to reading. By placing it in the empty spot left by the book, you’ll know exactly where to return the book to, and you will not cause undue wear and tear to the cover. As I stated in On Book Collecting, the first thing you should do to protect your books is to cover the dust jacket in a Brodart cover. This should be a boks first line of protection.
*Do not eat and read. Food stains and remnants not only reduce value, they practically beg for an infestation of insects.
Shelving: Books should be stored vertically; neither too tight on a shelf, nor too loose. When removing a book from a shelf, you should firmly grasp both sides of the book, and not grasp the top of the spine. This can lead to a binding falling apart quickly, especially with cheaply glued bindings. (Which are much too common in speculative fiction, especially UK editions.)
Book shelves should not strain under the weight of a full shelf. A strained shelf can work to warp a book and roll the spine. Books should never be pushed all the way to the back of the shelf. Leave a few inches of space behind your books for air.
*A clove or two per shelf, tucked in this free space between your books and the back of the shelf, will help keep insects away.
Barrister Book Cases: Valuable books should be stored in barrister book cases, or any sort of glass-doored book shelf. This helps keep out dust and dirt, and is the ideal way to store your most treasured tomes. A true barrister book case can be incredibly expensive, but cheaper glass covered book cases are available from places like IKEA for significantly less. These are infinitely more important if you have a smoker living in your home. Just as cigarette smoke yellows walls and décor, they yellow books and reduce value.
If Damage Occurs: Seek professional conservator help. Do not try to tape torn pages or re-glue a binding. You will only add to the damage.