I'm downloading a 101 MB EPUB from Anna’s Archive. I'm not sure if it's an official EPUB or someone converted it from something else. There's no PDF available there. In a few hours I'll try to report how several readers handled it.
There is a kindle version (which would be closer to epub than pdf) but it just is even worse than a pdf and the authors also include the reason for that:
> Due to the complex integration of images and text, this DK eBook has been formatted to retain the design of the print edition. As a result, all elements are fixed in place, but can easily be enlarged by using the pinch-to-zoom function.
EPUB is simply not ready for complex layouts.