By Alan Jacobs
No one really understands what a book is. Not so long ago we thought we did: a book was an easily recognizable object, sheets of paper gathered and bound on one side, usually with glue, sometimes with thread. Some kind of cover to protect the pages, made of cloth or thick paper or shiny card stock or (in exalted circumstances) leather was normal, though if the cover happened to be torn away the book was still recognizably a book.
Alas, we are already in difficulties.