Google Play Books has been our top pick for ereader on Android for a while. Now, it's getting a little better. The newest version of Play Books allows you to sync your notes, highlights and bookmarks to a separate folder in Google Drive.
The option is buried in the app's settings. Once you enable it, Play Books will create a folder in your Google Drive account and fill it with any notes or highlights you make while reading. You can duplicate the notes document and edit it as a regular Google Doc. This can be particularly handy if you're doing research or trying to track a complex story.