If you're unable to adjust the font size in the OverDrive app on an iPad (on iOS 10), this may be caused by an issue with iOS 10. Use the steps below to resolve the issue in the OverDrive app:

  1. Check the Apple App Store and make sure you've updated the OverDrive app to the latest version.
    • What's New in Version 3.5.7
      • Fixes a bug that prevents the font size from being changed on iPads running iOS 10. Having problems with font size in some books on iOS 10? See http://help.overdrive.com/customer/portal/articles/2574801 for help.
      • Fixes an issue where the wrong cover art would display for some titles.
  1. If the font size still doesn't change, open the eBook, tap the middle of the screen, then tap the Settings icon.
  2. Turn Default layout off, then try adjusting the font size.

Hope this helps.