First, thank you so much for creating this. Mozilla's decision to remove the native reader was unexpected.
I like this add-on because it is simple and does exactly one thing and does it well.
It took a little work, but I have imported the live bookmarks that Firefox auto-exported on the update to 64. I had problems with dupes but that seems to have died down. I used another add-on (Bookmark Dupes) to clean up the list and it seems stable now that it has finished the initial import.
Editing my review a couple of years later just to say this is still one of my favorite Firefox extensions. I have no idea why Mozilla took out the native support, but this is exactly what I need.
When researching the latest news, the ability to open every single story with "Open All in Tabs" is a time saver as well.