Originally Posted by dordale
In order to share DRM'ed books with your sister, you'd have to add her to your account. Then she'd have access to all the books in your library. But, be aware she'd also be able to buy books on your account (with your credit card) as well.
Not necessarily. He can activate/authorize her reader on his computer when she comes to visit or something. Once the reader is authorized, he can just share DRM'ed ePub/PDF with her (via email or SkyDrive or Dropbox or something) and she can just drag and drop DRM'ed ePub/PDF to her reader using any file manager.
Actually, since the DRM can be handled by Adobe Digital Editions and there are various ebook stores around that support Adobe ePub/PDF, he can use completely different log-ins for the purchases and activation.