What I find fascinating is the historical perspective: while still useful, the alphabetical index is hardly exciting anymore. It has been supplanted by full text search (in e-books). There are still reference books (such as dictionaries), but they are being replaced with online tools. Information overload continues to generate many inventions: the search engine (such as Google), the recommender system (as on Amazon.com), and the social networks (such as Twitter). Literally, these tools expand our minds. We become smarter.