Given the choice, which would you rather have...a hardback book missing pieces of the spine, the dustjacket and one or more pages that have been dogeared too frequently...or a Fine copy of the same book, with crisp, pristine pages, a straight and unsunned spine, and a bright, completely intact dustjacket?
Most folks, understandably enough, would opt for the latter. So would most scholars and the marketplace. But to insure that such condition is a commonplace in your home library, you need--when designing & planning your private library--to give a bit of thought to the slings and arrows of outrageous fortune to which books are prone.
Humidity, for example. If you live in a very humid environment (such as the southeastern U.S.), you easily could wind up with a private library of moldy, mildewed books...unless proper preventative care is taken.
Do you live on the West Coast of the U.S. or along the Pacific Rim (Japan, for example)? Welcome to earthquake country! Earthquakes are great for cocking spines or, worse, tossing every book you own into a massive, undifferentiated pile. Unless proper preventative care is taken.
Is your private library going to have bookshelves exposed to direct sunlight? Kiss your bright dustjackets and gilt-lettered spines goodbye! As anyone who has ever paid much attention to billboards or outdoor signage knows, direct sunlight fades colors quicker than just about anything. Do your books a favor...keep 'em in the dark! (Semi-dark also works, but--at the very least--out of direct sunlight.)
Wondering why the spine tops of your books look like someone has mashed 'em down? Consider how you take your books off the shelves...finger(s) to top of spine, pull firmly? Your book will survive in much better condition if you push in the books on either side of the book you want, then grasp the book you want firmly by its spinal midsection.
Chipped dustjackets, cocked or sunned spines, loose pages...all can be avoided with proper preventative care....