Books and shopping baskets. They really quite similar.
While shopping with my girlfriend yesterday, I held the basket while she picked them items and handed them to me. I asked her if it felt weird passing off the groceries and not carrying them into a basket or cart. She said that it did feel abstract. There’s something about the tangible nature of carrying a basket in the grocery store and feeling the weight of how much you selected.
The same can be said of print books. While reading, you can feel your how much you have read in the book. However, in an ebook, you you lose that sense of the tangible sense of how much you read.