Sometimes informally referred to as book mites or book lice, psocids are small, wingless, yellow insects. They prefer humid environments and usually are more interested in eating mould than your books. They are extremely sensitive to environmental conditions, so getting rid of them can be a simple matter of altering the environment slightly.
Remove the mites with a small brush. Deposit them into a sealed bag, and dispose of them.
Remove any mould growth, which the mites are naturally attracted to, by brushing it off or putting the mould in contact with sunlight.
Store these books in a dry, hot space, whose conditions will kill the remaining mites off naturally. Setting a dehumidifier near them to a humidity level below 50 per cent will deter the mites.
If the mites prove persistent, apply boric acid powder to them. Available in most pharmacies, boric acid powder should be used cautiously and in small doses.
Hire a heat treatment company to eliminate more relentless infestations.