The big advantage of ePub is that the text is reflowable, this is a great idea as it really helps towards device independence, but from what I’ve seen so far, the formatting doesn’t always come out as well as it could. Particularly the printed version doesn’t look very nice. It also suffers from the fact that it’s not natively supported by web browsers and users need to download one of many apps to read the file outside of the browser. The lack of a go-to app means that users have to decide which app they want to use. People are pressed for time and don’t want to do too much research or think too hard about what app to use. It might not be something that many technologists or tech-savvy users want to hear but generally, people want to know what the ‘standard’ or ‘regular’ app is.

Also related to the lack of native browser support is the fact that it doesn’t successfully bridge the gap between on-line and off-line computing. You have to make a conscious effort to download, save locally or onto your personal cloud account, like dropbox for example and then re-open it. It’s not seamless. Here’s a link to the draft of a white paper from Markus Gylling of IDPF, Ivan Herman of W3C and Tzviya Siegman of Wiley exploring a convergence between ePub and Web that would move towards convergence between offline and online. http://w3c.github.io/epubweb/

I’m a fan of ePub and I think that the successor of the PDF will build on some of it’s ideas. It’s possible that ePub may evolve into something with better mutlimedia support and online/offline functionality, but it doesn’t yet solve the problems that it needs to in order to really take off.