This add-on is a little bit wonky. It allows you to adjust font qualities, mostly; you can set up a dark mode, mostly; it remembers where you were in a EPUB, only if you set a bookmark. Nor does it have a library setting, convenient if you keep your ebooks in one place. Also, if you switch full-screen mode on or off, you will see that the reader does not adjust accordingly.

But it does read EPUBs at least as well as another wonky reader (Nook), so I am happy to cut it some slack and grant it five stars.

My initial frustration was relieved when I learned (RTFM) that there is a toolbar button to open locally stored epubs, making my reading MUCH easier and more enjoyable. Five star rating gladly granted.

It's great but it lacks of a dark mode

I think it's a really neat addon! However, whenever I do want to download an EPUB (which isnt too often) I don't have the choice to choose to download it. Also, sometimes it just doesn't load what I'm trying to read.

Extremely basic.
No page numbers, no settings, cant even scroll the pages using a mouse.

A extensão, me parece, aplica background-color: white por default, e acaba com qualquer box colorido que o e-book possa ter.

Only thing i intensely dislike about this reader is that if you mess up and close the tab, or have a crash, and you don't recall which ePub you're reading, there's no way to go back to it. Surely there should be a way to write a local state file that would remember the previous opened file and position. Setting a bookmark is fine, but doesn't solve this issue.
If that were solved, it would be 5*.
The other issue is that if highlighting and selecting text, if you're heading towards the margin rather than away and you go a tad too far it will can it as a next/previous page activation, even though there is no click. Easy to recover from, but annoying.

It's a nice extension that i would recommend. However, when i open a web adress that ends with .epub, the extension will intercept and try to open it (with error, of course).

Is there a way to temporarily disable this interception?

Exactly what I needed. Works as intended.