Converting these files is rarely as simple as changing a file extension; it usually requires "stripping" the DRM first. 1. Using Specialist Tools (e.g., z3kit or Epubor)
For tech-savvy users, there is a community-developed tool called Extractor.epub . This tool is essentially an EPUB file that you "sideload" into the VitalSource Bookshelf app itself. Once loaded, it can package the internal files of your book into a standard EPUB. vbk to epub
Simply copy the EPUB file from the restored backup to your local drive. You now have a standard eBook that can be opened with any EPUB reader (Calibre, Adobe Digital Editions, FBReader). Converting these files is rarely as simple as