Simple and works great. For articles with a show all button, you can activate the extension after clicking show all and it works. Only thing missing is a settings page, there is no settings button, no way to customise on mobile at least, and no way to pin it to the toolbar on Firefox Android. This means I need to open the article, tap options > extensions > ream which is a lot of tapping to enter reader mode. That's a shame, as otherwise it works beautifully! Still 5 stars as it's better and more versatile than the default Firefox reader mode.

The only thing missing is the ability to create website list for automatic reader mode switch

Simple and useful!