It's a reader all right, but it just opens the book, without an option to download/save it.

That's a massive problem.

good tool but drag and drop option for file opening would be nice to avoid time intensive searching in open dialog. Flaws with fullscreen mode (white empty areas at bottom with dark background). Read aloud addon does not work properly with this reader. (might be a Read aloud problem)

Perfect... EXCEPT for the fact it doesn't work in fullscreen

I would like to be able to use theming for day and night reading options

Funciona muy bien, pero antes permitia abrir los libros directamente del firefox de forma integrada, ahora solo se pueden abrir buscandolos desde examinar archivo. Deberían incluir nuevamente esa característica

Pratique mais un peu lent je trouve.

Не полностью поддерживает формат EPUB.

This is a good epub reader but I do wish that it could be configured as to whether or not previously read pages are listed in the browser's back button. (Right now it seems that they are with no option to disable that feature.)

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 works well to open files from a web link (HTTP://...). However, if I try to open local files (local hard drive or local network), I get endless "open with..." dialogs.
I found a dirty fix : when I open a file from the web, the address always starts with "moz-extension://697be157-ddf5-4bbd-bd58-56b42dd47af5/reader.html", so I bookmarked this address, and it launches a "blank" epubreader interface, from there I can click the top gray "open" menu, so I can browse my local computer manually. It would be a lot nicer if I could just double-click files from Windows Explorer.

It would be nice to make use of the speech synthesizer capacities to read the book out loud with speed controls