How long were horses used for transportation? There were no alternatives to paper books at all until personal computers and PDFs. E-book readers aren't perfect yet but they're the first real alternative to books.

The first real alternatives to horses included dogs, canoes, camels, donkeys, mules, travois, oxcarts, barges, hot air balloons, steam locomotives, bicycles, coal-dust-powered Diesel cars, biplanes, and zeppelins, before we got to the Model T.

The first real alternatives to paper books included papyrus, microfiche, reel-to-reel microfilm, card catalogs, Rolodex files, the khipu, the filmstrip, the erasable notebook of ivory leaves, the phonograph, Indecks cards...

Surely microfilm replaced paper books in many uses some time ago.

I think the last time I saw a horse being used for transportation (pulling a two-wheeled cart) was, uh, last week.

So it might be a lot messier than a simple replacement.

Books haven't been around for far longer because they are timeless, but just because it took a while for technology to become superior. We've passed that point and the transition is going to be swift.