Which may have many more users than this group had. How many users does a library in NYC serve?
Libraries have a limited number of physical copies to lend out.
These lending systems are much more limited: each copy can only be loaned once. http://www.amazon.com/gp/help/customer/display.html?nodeId=2...
To read the books in the library, you have to physically go there, check it out, and take it home (or read it there).
But back then you also had to physically go to a book store, buy the book and take it home. Borrowing wasn't much more difficult than buying.