: A versatile open-source reader that handles various ebook formats efficiently.

Which of these would be most helpful for your ?

: If the OneDrive app still functions on your build, upload books from your computer to the cloud and then "make available offline" on your Windows Phone. Recommended Reading Applications

Troubleshooting a that isn't opening your files.

Since the Store may be inaccessible, you should check if these apps are already installed or available via .XAP/.APPX sideloading: