Windows Phones can no longer download the OverDrive app from the Windows Store. If you've already downloaded the OverDrive app on your Windows Phone, please note that some users have reported trouble using their library's new OverDrive collection in the app, including borrowing and downloading books. Unfortunately, there is no solution for these problems with the OverDrive app.
You can still read library eBooks on your Windows Phone using the Kindle Book format (U.S. only). To do this, open your library's digital collection on your computer or another device, borrow an eBook, and send the Kindle Book format to the free Kindle reading app on your Windows Phone. You may need to look for library eBooks under your "archived items" in the Kindle app.