title_body: If I update an already published book on iTunes Producer, will those changes be pushed to purchasers? Similar to this question, but would like to know specifically if there's a way to do this through the iBookstore/iTunes Producer, and what the process might be.
  
  The books are epub2 and epub3, not iBooks Author.
upvoted_answer: Yes, this happens automatically.
  
  https://support.apple.com/kb/PH12101?locale=en_US
  
  
    During the publishing process, you specify whether the book is new or
    an update to a previously published version. If it is an update, you
    must provide a new version number. Readers who downloaded your book
    are notified in iBooks that a new version is available.