Saying books don’t go viral is flat-out wrong. Without the internet, books went viral and got passed around like the flu. Books are social by nature and shared and re-read until they fall to pieces (unless it is Bill Clinton’s memoir, in which case it is donated to a neighborhood coffee shop’s bookshelf.
The web does give us a different way to discuss books, before and after they are published. Books were always discussed, but perhaps only a fraction of that discussion made it to the writer – perhaps that is what this article is referring to.