title_body: Are ebooks licensed only to a certain email address?
upvoted_answer: I do disagree with idiotprogrammer's answer because this question does dive into DRM which plays a large part in ebooks.
  
  You could try changing the authorization of your Adobe Digital Editions account, reference: "How do I change the authorization on my laptop" with a re-install.
  
  If that doesn't work you would need to contact ebooks.com. Since you're getting a .acsm file I would 99% think they are using Adobe Content Server.  
  
  
    First, it's ridiculous to think that a DRMed ebook is tied to an
    email. Instead, it is tied to a user account created for a specific
    vendor. Every website under the sun allows you to change the email for
    the account. Even if the sign on you use is the email I suspect you
    will be able to change the email associated with it from account
    management on the user's site.
  
  
  Actually not..  ebooks.com might treat the email address as the ID and use it for validation to prevent transfer.
  
  Your issue will need to be addressed at the vendor if a re-install of ADE is unsuccessful.  To my recollection DRM is scoped to what they have identified as the ID.  In this case your ID is your email address.  You might be allowed to change your email address in the account settings of ebooks.com but I do not have an account there so I wouldn't know.
  
  I did run across this in research: "I figured out the .acsm problem!".