For me there are only two eBook readers that I need and use. The Kindle app, and the Google Play Books app. The latter is now offering you a way to save notes, highlights and bookmarks to Google Drive and make your life a little bit easier.
The feature is on the settings and you can easily activate it. Go to settings, select the option to save the notes to drive. Tick save my notes, highlights and bookmarks and hit OK.
Once that is done, the app will create a folder on Google Drive and you are set to go. Happy readings!
Source: Android Police