It's interesting that you mention the origins of book distribution -- buying the block, then getting it bound, etc. Two of my favorite writers from about that time are Sterne and Pope, and they both write sometimes about writing and being writers back in the 18th century, and they mention subscriptions and such things.
I have this vision of the business once upon a time -- At some point, I think publishers became a sort of "Jim Likes It" list of books filtered through the tastes of the person(s) whose name was on the letterhead -- Houghton Mifflin, Macmillan, Little Brown (*reflexively adds Jug*), Charles Scribner, etc. But earlier, it seemed not so much that publishers were the arbiters of taste as that writers convinced publishers that their books would sell.
But both Pope and Sterne sometimes hint about writers, especially new ones, building their own readerships through subscriptions that amounted to pre-ordering. It suggests that a publisher, who was laying out the cash, had to be assured of a minimum number of sales before he'd pay for a first press run. I suppose this would be especially true of books that were released in serial volumes. But it does seem to me that, back in the day, writers were primarily their own main promoters and marketers.
It seems to me like the publishing industry model through the industrial age, 19th and 20th centuries, was heavily dependent on the distribution structure. If that structure changes radically, does that entire model go away? Are we dialed back to the pre-industrial or proto-industrial writing business of the 1700s as our starting point? Should we be looking at how books were sold then and think about transferring that model to 21st century tech?