The fact that I have to have a full WebKit process and actual JS running just to view an EPUB is really infuriating.
Can’t anything just be a ruddy DOCUMENT format anymore‽
To be fair: EPUB is actually a good use-case for semantic XHTML5, WAI-ARIA, DPUB-ARIA, MathML, and RDF serializations. This does call for some sort of web engine, but not necessarily a complete browser engine capable of running web apps.
Most of the rest of the Web platform beyond semantic markup and simple stylesheets should probably be stripped away from a typical EPUB reader. Unfortunately, few “slim” engines actually support enough of the features I described. Engines like Ultralight (proprietary) and litehtml come to mind, but I don’t know how good the latter’s accessibility support is.
I very much agree that JavaScript support in EPUB was a mistake; fortunately, it’s seldom necessary. Signed JIT-less JavaScript as part of the e-reader program should be okay, as the user consented to run it.