Also, ePub format is really easy to read even without a specific e-reader. Just unzip it and look for files with names ending in .htm, .html or .xhtml, and open them in a web browser. OK, you'll lose the special formatting and navigation features but they aren't esential.

(That's non-DRM ePub format. DRM you may be pushed to find a reader. But D's current books are DRM-free and I think she intends to keep it that way.)