There's something of a rush these days to design the "killer" comic book app for PDAs or smart phones or something. I'm here to tell you, though, that they won't work. Any of them. See, there's an inherent problem with the basic premise: the screen size is WAY too small to read comics.
Think about how much screen real estate you have with any of those hand-held gadgets. Maybe 2 by 3 inches? You can only get one or two comic panels in that space and maintain legibility. Even if you had an incredible screen resolution, you'd still be stuck at one or two panels at a time, just because the text would be too small to read for most people if you tried to get any more on the screen at one time.
"So?" you're thinking. "Sure, you wouldn't be able to read the whole page at once, but as long as there was a good navigation system, you could do one panel at a time."
How long does it take you to read a comic panel? One or two seconds? Then what? You'd have to scroll/click/slide/whatever to the next panel. Then you spend another second or two reading that panel, and then you'd have to scroll/click/slide/whatever to the third one. You'd end up spending as much time navigating the document as you would reading. And that's an inherent problem for two reasons: 1) the reader is constantly being removed from the story in order to manipulate the delivery object, and 2) the reader would increase the amount of time interacting with the comic, but spend a significantly portion of the time engaging the comic. That last one sounds like semantics, but it's a note-worthy point, I think.
When a user "interacts" with the comic, they're picking up their iPhone, loading the comic, reading a panel, clicking to the next one, reading a panel, clicking to the next one, etc. That's a lot of interaction, but most of it (the loading process, the clicking) is not "engaging" the comic. If a user, for example, would normally spend 15 minutes reading a comic, they might increase that time to 20-25 minutes if they had to click between each panel. But since the clicking is not part of the story (as is the case with video games) the reader essentially wastes an extra 5-10 minutes for each comic.
I don't know exactly where the market for transportable digital comics is going, but I know that most people won't tolerate the click/read/click/read/click read methodology. The delivery mechanism will need to be larger enough to get several panels on the screen at once, suggesting something more akin to a tablet PC.
That said, though, I'm thinking that the letter-size format most tablets resort to isn't exactly necessary, but you would need something with a screen at least the size of the Kindle's (roughly four by five inches) to even start making digital comics reading viable to mass audiences (well, "mass" being relative to existing comics readership). Tablets seem to work reasonably well, but they're collectively still a tad too bulky to make extended reading comfortable.
Somebody let me know when Fujitsu's FLEPia is available.