A climate-controlled or climate-controllable environment, a room, or a vault
Step1
Protect your books from prying hands. Human use is the biggest threat to keeping antique books in good condition. Specifically, when the books must be handled, the cover and binding should be supported as much as possible. These areas are under a lot of pressure when the book is opened.
Step2
Control heat. The environment of these books should be around room temperature and relatively static.
Step3
Control humidity. Some recommend using a dehumidifier to make sure the books aren't in a humid environment. However, too much dryness is also bad. The more control over humidity, the better.
Step4
Keep your antique books in the dark. Despite sounding kind of sinister, this is a necessary step to maintain your books, as light dries out the books and causes print to fade.
Step5
Repair bindings only under expert supervision. It may be tempting to glue pages and bindings back together, but usually, a novice will end up spoiling more than he/she fixes. Book binding experts will know how to fix the pages of your antique books to the cover and binding the right way.
Tips & Warnings
Research chemicals before using them to preserve antique books. All kinds of solvents that may be sold to repair old books can actually damage them.