Customizable reader mode, 'nuff said.
Basically what Firefox used to have before they removed it.

Needed this for Reddit, it didn't work. (Only shows description in reader view and shows no posts.) Might work for other things.

It's a definite improvement on Firefox's own reader view, and very customizable.

I have some vision problems and this add-on really helps.

I also use this to quickly convert articles into pretty looking documents that I can print, or save as PDF for my e-reader.

Wonderful options visually, but the text-to-speech is currently broken, at least for me.

I was trying to skip ahead to later in a page and it would only play from the beginning. Even waiting it out didn't help because it would read the first few paragraphs and then stop.

Best tool for reading view

This is the best readability add-on for Firefox at the moment - it's reliable (doesn't remove the full article LOL, like for instance the Clearly Reader add-on does), its editor funcitonality is top-notch, and the default reader layout is just beautiful and calming.

I like the address bar icon instead of the toolbar icon.

The new update disabled the icon in the address bar, now it's just a simple + icon next to the other addons.

It's better than default reader view, but auto switching is very buggy and on most pages doesn't work. I go back to default reader and Automatic Reader View add-on.

I was searching for alternatives to default Reader Mode of Firefox browser because on forum Sufficient Velocity it works in a really wonky way making it completely unusable. There is some weird interaction with "Threadmark" function of Sufficient Velocity forum that causes (Default) Reader Mode to fetch text from always the wrong post (either last or the next one).
This addon solves that problem thanks to option to manually direct the source of fetched data through highlighting the correct post bypassing the weird interactions. Exactly what I was looking for!