Books are easily soiled and food residue attracts vermin. Keep books dry in wet weather. Have a plastic bag available. Don't read library books in the bathtub. Wet books quickly become mildewed.
Mildew spreads through books like the plague and presents a serious health risk to some people.
Use bookends When books lean, their bindings are torqued and weakened. A book that is not shelved properly can pull itself out of its binding. If books are too tall to stand upright, shelve them so their spine is down. If the spine is shelved up, the textblock hangs unsupported and will tear itself out of the binding. Don't smash the binding onto the glass.