As a long-time Sage user, this add-on looked like just what I was looking for on Firefox 57. However, right now its functionality is very limited. My biggest issue is that the reader doesn't notify you of new/unread feed items in any way. It simply gives you a list of items to click through with no way of telling whether you've already viewed them or not. I will be monitoring this add-on because it looks like it could have potential, but in its current state it's just not very useful as a feed reader.