I don't see how reading manga on an E-ink ereader, with one page filling the screen and "turning" pages by pressing the right side, is fundamentally different from reading it in "analog" (paper) form.

I wouldn't want to read it on a non E-ink screen, or have to scroll within a single page though.

Parent probably was referring to reading it on a laptop or similar, which many people do. (I also read it this way).

I use the SimpleComic reader on OSX, first removing the menu and then fullscreening it. This requires me to download the manga beforehand. It works for me since I don't read that much manga.

Now that I have an ipad I wonder how well it could work.

Yeah, that's not true at all. Manga on a 8-10 inch-tablet can be far superiour to the poor paper manga are usually sold at. Though it's true that it also depends on the reading-app/service.

Do you know if there's an ipad app that easily lets you upload manga via zip files?

Sorry, I 'don't use iOS. I have an Android-Tablet.

But short search says "Manga Storm CBR" is according to your demand. Search for cbr, which is the common fileformat for comic-archives. You can also widen the search and search for comic-apps or reader-apps in general. Manga seems to be often a bit to specific in those cases.