[Mug Funky]

subtitles would be pretty ugly to read. however, if you made the book as flat menus you'd be able to do it. sub streams could be useful if you're into multilingual books.

but for menus to be nicely readible on a 720x576 or 720x480 screen you wouldn't be putting too many words per page. also, i wouldn't want to be stuck with the job of authoring such a DVD (or author-checking it). though there's the possiblilty of a tool that authors the flats for you using a directory full of numbered images and a template subpic for navigation (like a left and right pointing arrow at the bottom right of each flat picture).

additionally you could have 8 audio tracks in different languages, but that would mean giving up on flat menus and using low bitrate video. even if the video was structured as 1 high-rate i-frame followed by a GOP with all blocks encoded as "skip blocks", the video would still be a pretty high bitrate compared to flat pictures. it'd also be a problem timing the audio part with people's average reading speed.

all in all, i think e-books are a better idea. though portable DVD players that can also read regular e-books would be pretty cool.