Once upon a time, an author had to directly solicit pre-sales for his own book. Those who bought in were subscribing to the book.
From the 1770 book, Antiquity [Google Books link], we see how this worked out in the finished product.
And you would also get a numbered edition, perhaps with an inscription too:
Frankly, I’m exhausted just considering how many times Jonathan Brooks had to pitch his book. Over and over and over again.
And his subscribers wound up having their names displayed two hundred and forty-three years in the future, digitally, on screens around the world.
Mike Cane’s xBlog 
Setting the type for that list of subscribers was not trivial either.
1st Language
2nd Writing
3rd Papyrus
4th Paper
5th Books
6th The press
7th Internet
8th The web
These are all integrated technologies that serve us today as communication system and took thousands of years to create.
This comment is possible due to this integration.
Erm, between Writing and Papyrus should have been clay tablets. Stone tablets too, if you want to count the Old Testament ones.
1st Language
2nd Writing
3rd Clay tablets
4th Stone tablets
5th Papyrus
6th Paper
7th Books
8th The press
9th Internet
10th The web
Between 8 and 9 was teletext, which actually lived on in England until I think last year. There were several teletext and videotex (no T at the end) initiatives in the US. Time Inc actually planned and was testing a ginormous teletext service for the US but it never went anywhere. They’d probably be in better shape today if it had. And pre-Net, American farmers were subscribing to the ProFarmer service, which provided agriculture-related news. And let’s not forget Minitel in France. There was online before anyone had ever heard of the Internet. Hell, I didn’t even mention The Source and CompuServe, which both had news (AP was on both, I think; maybe UPI too) and forums. And CompuServe had pre-Twitter with its CB Simulator.
I think somewhere between 4th and 6th would be Vellum
1st Language
2nd Writing
3rd Clay tablets
4th Stone tablets
5th Vellum
6th Papyrus
7th Paper
8th Books
9th The press
10th Teletext
11th Internet
12th The web
13th Synthetic Optical Telepathy
And don’t forget the invention and then development of printing – Johannes Gutenberg for the moveable type press, Alois Senefelder for lithography, Richard March Hoe for the rotary press and James Bibby for flexography….