Source: http://www.engadget.com/2013/10/29/amazon-matchbook-live/
Amazon's Matchbook service, which offers e-book versions of hard copies of books like Amazon's Autorip offers digital versions of physical music, is now live. The service supports over 70,000 books at launch with digital equivalents costing $3 or less. The service recognizes purchases from as far as 1995 (when Amazon first started selling books), and their digital versions come with all the bells and whistles readers have come to expect from the Kindle service: Whispersync, X-Ray and more. Of course, Amazon's promising that there's "more being added every day" to the list of available titles, so don't lose all hope if you don't see your favorite authors/publishers/etc. listed.
Source: Amazon