Books offer an infinite variety, are easily wrapped, can be personalized for the recipient and are displayed as a symbol of one's own identity. They are, in many ways, the quintessential gift for Christmas, Hanukkah or Kwanzaa or another gift celebrating December. Books are great gifts because they have a special meaning for both the person who gives them and the person who receives them. Giving someone a book shows that you care.
I love that you can also add a personalized message inside the gift.