Even in an age of digital reading, printed books are still in demand. If you're looking to make room on your bookshelf, donate your old books. The rule of thumb for donating books is this: If the book has been in print for only two or three years, donate it to your local library, which will resell the book at a fundraiser. If it's older than that, donate it to the Salvation Army or Goodwill, where the books will be sold in the store. No matter how you donate your books, be sure to get a receipt for tax deduction purposes.