Books were designed to be stored horizontally in small stacks. That not being very practical, storing them upright is the next best thing. Books get damaged when standing at an angle, as pressure is exerted unevenly on their structure causing them to become deformed or crooked.
Books on a shelf support each other, so it is a good idea to sort them by size whenever possible. Tall skinny books next to short ones will end up leaning into the empty space, becoming bent and distorted. If sorting them by size is unfeasible, tall books can be supported with rigid boards to prevent them from becoming distorted. Here’s a handy “book splint” tutorial we prepared earlier.
The curved bit at the top of book spines is fragile. When pulling books from the shelf, they need to be grabbed from the middle area, shuffling adjacent books a bit and grabbing the covers, never the spine. A lot of damage to book spines can be prevented this way.
Light causes inks to fade and damages book covering materials like cloth and leather. Books are therefore best kept away from the light, especially if stacked unevenly, allowing light to reach only parts of their covers and causing covers to fade unevenly.
Most books are unable to be opened to 180 degrees. Pages will spring up if books are laid flat on a surface and keep trying to close up. Many books also have damaged spines that only become worse if pressed against a hard table. Pillows are used to reduce the opening angle, reducing strain on the binding and preventing pages from springing up. An under filled pillow, folded fabric or rolled up towel can be used, supporting both sides of the book, or just one.