jayskette they should just add what toys are appropriate and what are not, on the tags.
Unfortunately, books should never be seen as inappropriate.
BUT it isn't charity that chooses what toy goes to what kid. I remember going along with a friend of mine to drive her to the Salvos and pick up her presents.
There were 2 rooms packed full of toys, sorted according to age. The parents were the ones who were allowed to choose 1 item per table. There was a table with books, but at the end of the day, most toys were gone but the books were all still there.
So it is the parents greediness and ignorance that makes books "unwanted" by charities