BookRiot: “Anyone who has ever tried to organize their bookshelves can tell you that books are not a standard size. In fact, even books that fall under the same category (mass market paperbacks, trade paperbacks, hardcovers) can vary wildly. It makes a perfectly matched shelf very difficult. Despite all of those different sizes, though, almost all books have a certain proportion. From books that could hang off your keychain to dictionaries you can hardly lift, they are almost always rectangles taller than they are wide, at around the same proportions (width:height of about 5:8). And this isn’t a new invention of mass printing: according to The Book by Keith Houston, the oldest books in the world have about the same proportions, though they were often slightly taller than our books now…”