April 3rd, 1995 when the first ever book was ordered online on a then-unknown website called Amazon.com , little did anyone know that soon we would witness an incredible experience of digital reading and learning. That we would get a book the moment we ‘desire’ and carry with ourselves thousands of books in a little device. That books will no longer be measured in pages but bytes. That we wouldn’t actually have to read the book to ‘read’ the book – we would just listen to it without anyone’s help. That anyone would be able to publish a book in few clicks and you will be recommended the best of the books by a machine which would have otherwise been an unknown unknown for you.
Welcome to the digital ecosystem of reading.
As the industry transformed from print media to digital content we witnessed quite a few companies who emerged as winners whereas the other established ones struggled to stay in the game. The whole ecosystem of reading has evolved in 4 dimensions:
As more and more physical books started getting sold online, Amazon released the first Kindle in 2004 – a device that enabled users to browse, buy, download and read e-books, newspapers, magazines and other digital media via wireless networking to the Kindle Store.  The product was sold out in 6 hours.  The ability to get the book immediately with just few clicks and to set the font large or small as per own comfort, provided instant gratification to users who could now have thousands of books stored in Kindle and carry them anywhere they want. The subsequent versions of Kindle enabled users to use the product on the beach, underwater, darkness, bright sunshine with a perfect look and feel of reading a book. By 2010, Amazon was selling more e-books than hardcovers. As of date there are multiple ebook readers prevailing in the market – kobo, nook, ibook on ipad etc.
In early 2000s, companies like audible, simply audiobooks etc. launched ‘talking books’ that read out the book for you. Users could now listen to their favorite book while driving, physically moving or just when they don’t want to take the pains of reading. People could also rent the audiobooks if they didn’t want to pay the full price to keep it forever. This made reading (or listening) books much more efficient than before.
As an obvious next step, to cater to the need of sharing and recommending books to one another, companies like goodreads emerged in 2006 – a ‘social cataloging’ website that allowed individuals to freely search its database of books, annotations, and reviews. Sharing what you are reading and helping other book readers through online reviews and recommendation closed the loop for book reader who could now buy online, read whenever they want and get recommendations on their next book.
Another extension of matching phenomena was captured by Booktrib who gave an opportunity to lesser known authors to reach out to vivid readers. 
Goodreads members growth 2007-2013  
In 2005, Amazon further pushed the boundaries of reading world by allowing every individual to publish their own book in minutes. While established and conventional publishing houses were very selective in choosing their next publication, Amazon once again captured the tail authors who never got a chance to publish their work so far but now could self-publish it with few clicks and printing was on demand which means book was only printed once actual order was received on Amazon book store . Recently Amazon has moved from Create space to Kindle Direct Publishing to integrating the publishing feature within the Kindle ecosystem. The ebook version of the book can now be made available on Kindle Store or Amazon book store in minutes.
How is the tremendous value created, captured?
Many companies have come up with a subscription based model where users pay a monthly fee to have limited or unlimited access to the content. There is also a free subscription model that supports ads relevant to the reading profile of the user. Moreover, the cross-selling based on reading history and other data captured has tremendously helped to increase the revenues.
BookWorld, founded in 1976, closed its 45 stores in the US in 2017-2018.  Barnes & Noble
Borders Group, founded in 1971, filed for Chapter 11 Bankruptcy protection liquidating 399 stores in 2011  and was finally acquired by Barnes&Noble – the last standing national bookstore which is also now struggling to sustain itself. The brand has lost $1B in value since 2013 
While print publication definitely got cannibalized by ebooks , The traditional publishing industry has largely reshaped embracing the digital publishing that has helped the publishers to adapt to this change and maintain business continuity . Whether it is a print book or ebook, authors still need publishers to design and market the book which is a major chunk of cost in any book publishing . Having said that, the power is definitely getting drifted from Big 5 publishers to Self-publishers and indie publishers.
Market Share by major publishing categories 
The phenomena of print to digital is not just limited to book but we also see the shift happening in other publications – newspapers, magazines etc. The UK’s national newspaper, The Independent, went 100% digital in 2016 . The whole ecosystem of reading that the digital world brings to a reader makes the rise of the innovative concepts like audible, goodreads and KDP inevitable and it will be interesting to see what is next in store for us that will make reading, one of the favourite pastime of people, more convenient, efficient, connected and fun.
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