The App says it's unable to open?
If you don't mind losing app data, then you can Archive and Unarchive it. Note: You might also lose books in Overdrive and have to redownload them.
Press and hold on icon for a few seconds. In Menu that comes up choose Archive.
At top right on Library Page is 'My Stuff'. Tap on it and then in dropdown tap on 'Archived Items'.
Find Overdrive App and tap and hold on it. In menu that comes up tap on 'Unarchive'.