Thorium is astoundingly slow. I've started using Sumatra for ebooks as well as PDFs. It's fast and good enough.

Really wish it was a Chromium extension (or PWA) rather than separate app.

Really? Why on earth?

Since 90+% of the time I have the browser open. An epub book is just a weird, constrained website, another type of document to read.

Not saying there shouldn't be an app for those who want it.

Is it more than just an ePub reader? You really feel it’s justified to spin-up an electorn app (!!!) to read an ePub? I use Emacs’ nov.el or Foliate which are not only low on resources but also instantaneous to open files.

I don't like it either, but the only way it is technically feasible to support the full potential styling/markup of an EPUB is to use a browser engine, and therefore electron is a logical choice. Can your specialized EPUB reader support MathML? Or vertical-ttb text?

Just this. Epub depends on the same tech stack as the web. So, either you use an engine that supports that in full, or you are going to be missing pieces of the standard. Which means that most other reading software opts for missing pieces of the standard.

An .epub is literally a zip of xhtml, css, and images.

If you want to build a good ereader, you either use a web browser or you reimplement one. And you have to support things like https://developer.mozilla.org/en-US/docs/Web/CSS/hyphens, rtl, mathml, and—well—the rest of the nontrivial stack.

I have a bad news for you, recently I was interested in how could I write a good QML/Kirigami based ebook reader and looked at all the existing Linux epub reader and each one was using a webview for the epub rendering. But they usually try to integrate better with the rest of the app and your DE so you just don't see it.

EDIT: the only epub reader I know that doesn't use a webview is Okular and the rendering using QTextDocument basic html support is horrible.

Koreader and coolreader both based on crengine and dont use webview. Koreader devs forked crengine and now seem to be in the process of merging back. https://github.com/koreader/koreader https://github.com/buggins/coolreader

I ran into a similar realization when I set out to build my own minimal RSS reader.

Your options are A) web view, B) crappy RSS reader.

It's irrelevant to me whether or not it's an electron app. I'm not running a Pentium 486 system. I've got more RAM than I know what to do with...I'll run a half-dozen instances of Thorium if I wanted to...no worries.

It’s not just resources. It’s usability. Electron apps look and feel out of place to me. I would personally never use one let alone for reading an ePub. I get the point about perfect rendering, but that’s a specific problem I’m personally not worried about.