Just a few months ago in April, Microsoft announced it would be shutting down its DRM-locked eBook store. On Monday, July 1st, it will finally shut down the DRM servers that allow people to read the books they purchased [boingboing.net] there.
According to Microsoft's FAQ on the shutdown [microsoft.com]
What happens to books I've already purchased?
You can continue to read books you've purchased until July 2019 when they will no longer be available, and you will receive a full refund of the original purchase price.
There's more - even free ebooks will go away
What happens to my free books?
You can continue to read free books you've downloaded until July 2019 when they will no longer be accessible.
This also applies if the book is out of copyright, free, or has been annotated with your own notes and research.
According to author Cory Doctorow, who predicted this very event in a speech to Microsoft Research 15 years ago [craphound.com]:
This puts the difference between DRM-locked media and unencumbered media into sharp contrast. I have bought a lot of MP3s over the years, thousands of them, and many of the retailers I purchased from are long gone, but I still have the MP3s. Likewise, I have bought many books from long-defunct booksellers and even defunct publishers, but I still own those books.
In the event a purchaser still has the same credit card they purchased an eBook from Microsoft with up to seven years ago, refunds for the original purchase price (not inflation adjusted) will be credited back to it. Those that do not still have the original purchase mechanism on file will receive a credit on the same virtual store that is removing their books.
Cold comfort considering a virtual book burning won't keep you very warm.