Booklice are not associated with dirt or poor hygiene, but they are attracted to, and feed on mould. This could be the mould on damp, caused by fresh plaster drying out or not enough ventilation in a room, or a leaking tap; or it could be the microscopic mould that grows on the glue of book bindings or cardboard, such as in packets and cereal boxes.
The best solution for effective booklice control is ventilation. Throw away any infested items, wipe away any visible mould and thoroughly ventilate and dry out the area. A dehumidifier can help with this process. Insecticidal booklice control sprays will minimize the problem, but because booklice can be very widespread, removing the conditions they thrive in is by far the best course of action.