Mozilla has already mentioned about Reader View keyboard shortcut in Firefox 50 release notes, except for the release notes, you don’t know about the shortcut as Firefox doesn’t display it in the menu, now it does in the View menu when the Reader mode’s book icon appears in the URL bar. Target milestone for this change has been set to land in Firefox 54.

In Firefox browser, press Alt for File menu to appear on Windows.

View >  ‘ Enter Reader View Ctrl+Alt+R ‘

View >  ‘Close Reader View Ctrl+Alt+R ‘

What’s your take on this improvement?