Other commentators already mentioned it's the best you can find.
Idi0t proof & just work.

I love this addon i would give it 5 stars, but not everyone uses a light colored theme. Im using the Mozzila Edge theme, which is nearly black. I see in settings theres an option to change icon text red, that doesnt work either. it would be nice to have an option to have white. i never know exactly what my text level is unless its reset back to 100%.

The best since the old NoSquint. Web Extensions ready too.

This is the best text zooming addon you can find. It does the job easily without messing up functionality like zooming an image with a scroll wheel. It has per site text zoom and default text zoom. The only thing was that it required me to go into about:config to enable per site zooming.

Don't work on Firefox for Android 48.0, although for android.