Has Amazon turned ebooks into commodities?

For a long time, publishers and readers have argued that each book is unique and thus one cannot substitute, say, a book by Dean Koontz for one by Stephen King. For years I accepted that — until ebooks and agency pricing and Amazon exclusivity. Now, in the case of fiction at least, I think the tides have turned and ebooks demonstrate books and authors are substitutable, that is, (fiction) books are commodities.