Timothy Young writing in Design Observer, gives ten good reasons the book is important:  

7. A book is an object fixed in time. 
A book can tell us about its status in history. If we look through first editions of  Moby Dick or  Leaves of Grass, we find that they give away information not only about when they were created, but also about the worlds in which they were created, by way of advertisements, bindings, the quality of their paper, and watermarks on that paper. Such components are often not captured by scanning or are flattened out to make them of negligible use. In Nicholson Baker’s  Double Fold—his saga about how libraries microfilmed runs of newspapers in the 1950s and 1960s and then discarded them—one of his chief complaints was that the filmers skipped advertising supplements and cartoons: things that had been deemed unimportant.