If you know what books someone read and the history of all websites she visited you could get the correlation between her book reading experience and online experience. This is a valuable piece of information that can be sourced and built by an independent data aggregation team or company. Books drive search as I said in one of my last article news drive searches. Books like news drive search so knowing the relationship between book and search is a good perspective feature or a signal that could tell us how to improve books or search for the benefit of people. Book reader's requirements about search online are not the same as usual internet users.
Readers as the core audience