@Mathias The head librarian explained to me there were usually some books & DVDs they received a TON of and it didn't make sense to add them to the collection. If a book was a bestseller you could bet a lot of them would be donated after being read. People were also eager to get rid of magazines and DVDs. They would usually sell the books & DVDs for $1 and the magazines for 10¢ each.
@divisionbyzero If they keep them or sell them it's still good for the Library.
My local library gave me Goodwill as one suggestion.
With the money they pay their executives and the little they pay regular workers, I would rather NOT donate to Goodwill.