Hellsbelles
It would really help charity shop volunteers to bag up two lots when sorting out. One would be your decent, wearable items and the other marked up as rags. That way they don't have to bother sorting all the bags out. ( Just check beforehand they do send unwanteds to ragging )
I've done that because they get paid by weight by the ragman.
Ours are not keen on taking books either, particularly paperbacks although the Oxfam shop does a deal with a local antiquarian bookseller if anything is of value.
It's sheer laziness to just dump unsaleable items on charity shops.