@jimniels My WordPress plugin Friends can do this together with my other plugin Send to E-reader. When a new article arrives in an RSS feed it would send an email with the ePub of the article that includes it’s images. I also have another plugin for it called Post Collection which can download the articles images to the WordPress media library and rewrite the html so that if that article goes offline some day. That’s not fully offline though, it’d just all be inside your WordPress install.

Here is a demo: https://www.youtube.com/watch?v=kHaODAUazwE