Further to Good news! The Internet is worse for bookstores than for reading, Part I: (Dust settled, many books and readers have crawled out alive.)
The big difference is that the Internet changed how authors and readers find each other.
Some key changes were not intuitive. For example, many placed high hopes in putting great books online. As Richard Seltzer put it in Samizdat,,

Already there are tens of thousands of books in plain text electronic form available for free over the Internet, thanks to volunteer projects like Gutenberg. But while I applaud those efforts and download many of those texts, I must admit that I rarely read them -- only when I haven't been able to find a print edition of the same book. That's partly a matter of habit and largely a matter of eye balls -- it just isn't comfortable yet either with regard to the experience of text on a screen or portability. My eyes get tired when trying to read something lengthy -- so I'm inclined to print out the articles and book chapters I come across on the Web. Also, my laptop's batteries run down too fast, and my palm's screen and type size are a nuisance for anything but short messages.

Put another way, the fact that a text is on the Internet does not mean it is functionally more available. It is still only theoretically more available. More work is needed.
But Seltzer goes on to note a change that did make a difference: Internet book distribution enabled the success of some books to be predicted before they were printed or shipped:

… the new Harry Potter book was the number one best seller at Amazon, even though it had not yet been published. This was truly extraordinary. Books are usually not purchased in advance of being manufactured. It's usually a wild gambling game on the part of the publisher -- guessing how many will sell, printing that number, shipping them off to distributors and stores, hoping that they get shelf space and visibility and word of mouth, and then having those distributors and stores return unsold copies for full credit.

Accurate predictions reduce waste over time, which should result in lower overall pricing.
Note however, that far from obliterating the author whose book will sell only 300 copies, the Internet has greatly helped her:

Typesetting has become a matter of converting ordinary word processing files. And the machines used for printing and binding have become so flexible, thanks to computer control, that it is no longer necessary to print thousands of copies of the same thing at the same time to drive down manufacturing costs. In fact, it is now possible to economically print and bind a single copy of a book.

Exactly. Digitization and Internet transmission mean that both Harry Potter and Beloved Grandma Frankie’s Cookbook can both reach those who care, whether they are thirty million or thirty in number.
But what of those who must make their living from writing, manufacturing, and distributing books? Evan Hughes addresses that in “Books Don't Want to Be Free” (The New Republic, 2013):

If you’re in the business of selling journalism, moving images, or music, you have seen your work stripped of value by the digital revolution. Translate anything into ones and zeroes, and it gets easier to steal and harder to sell at a sustainable price. Yet people remain willing to fork over a decent sum for books, whether in print or in electronic form.

As he explains, the big problem for other media is that they can be disaggregated, cut up into little pieces and sold separately. But few buy only one chapter of a book. You buy the book or else you don’t. So the seller retains some control over pricing, compared, say, to the seller of an album with only one hit song on it.
Another factor, which Hughes notes, is that books are essentially ideas rendered in a typeface. So you can’t pay less to get an inferior version, the way you can pay less to watch a film on DVD instead of taking everyone to the theatre to watch it on wide screen. Internet-based book ordering, whether the product is print or digital, does not usually change the quality of the product in the same way.
Now here is a really interesting factoid noted last year at Forbes:

$5.25 billion: Amazon’s current annual revenue from book sales, according to one of Packer’s sources. That means books account for 7% of the company’s $75 billion in total yearly revenue.

But remember, at one time, most books sold in the United States were sold through department stores. Is there a good reason to believe that books accounted for even that much of such stores’ revenue back then? So maybe video killed the radio star, as the song claims, but the Internet has decidedly not killed books.
So, come to think of it, why did video kill the radio star? And how did the Internet affect broadcasting? Let’s look at that next. Note: I use American figures because they are easily available, and probably reasonably accurate. Local cultural conditions may make a difference, of course. In Canada, for example, many books of regional history are published on Canada Council grants. The accepted public benefit of preserving a history outweighs economic considerations.
 

Denyse O’Leary is a Canadian journalist, author, and blogger.