Almost perfect. Some options for the code would be useful (medium.com as an example)

I've tested many apps to find one that reduces the page to text. Tranquillity reader works without exception on all pages that didn't work with other readview-apps.

A reader view add-on/extension that actually works flawlessly! I rate this 10 stars out of 5! LOL

This add-on has been great. My one concern is that I am unable to change the font using an Android phone and tablet. I've been trying to change the used font from the default to Times New Roman. The changes take effect on the desktop-based add-ons, but my one reservation is Android. Overall, amazing app.

The only reader extension that provides the option to force text-align: justify. If it were the default, I would give six stars ;)

2019-01-11 Original 4-star review:
Excellent add-on, but I am seeing a slight problem with Win7/SP1/x64 & FF64. When I click on the icon to go into the Tranquility mode, just before the mode is switched, the original page zoom gets reset to 100%. Naturally, when I close the Tranquility mode and go back to the original page, my preferred custom zoom factor is now 100%. I am not using any zoom-control add-ons - just the built-in/stock functionality of Firefox.
Thank you!

2019-09-05 Update:
The zoom problem makes this extension completely unusable for me. The problem has not been fixed, and the developer has not commented on my bug report, so I am lowering my rating accordingly.

2020-02-08 Update:
Firstly, thank you for your response and explanations.
Secondly, I have found a workaround for the zoom problem. Essentially, zoom can be successfully restored by the extension "Zoom for Firefox" by Stefan vd. The latter's Zoom Engine must be set to "Use the built-in browser zoom", and some non-default zoom level must be in effect. I am therefore re-adjusting my rating.
BTW, maybe something useful could be gleaned from the code of add-ons "Zoom for Firefox", "Zoom Page WE", or "Custom Page Zoom". But like you said, maybe the code is too complicated to carry over.
Thank you once again!

2020-11-07 Update:
I have just noticed that the new Tranquility version no longer resets the zoom level. Thank you for your workaround - and for keeping me (well, all users, of course) updated on this matter. This must be the longest back-and-forth exchange done in a review! :-) I have adjusted my rating back to 5 stars. Thank you once again for your excellent add-on!

So far it works fairly well. I’m using the older 2.0 version under Firefox Portable Legacy so I can use the older extensions. The only feature I would like is to be able to load the Tranquility Reader page in a new tab or at least be able to get back to the original page via clicking back in the browser.

Simply the best. Thanks.

Давно искал замену встроенного ридера, так как там не работают переводчики текста.

Very good.