Bad idea, all around.
Handheld ebook readers still only do black and white, and are horrible for photos and graphics.
In the US they are only black and white.
In Japan color is already on the market.
Look for color to hit the US market in 2011 (we are always behind Japan and Korea now - thank you FCC).
Electronic paper is not the only way to view a textbook - laptops and netbooks are ubiquitous.
I prefer a tablet PC myself - here is what I use:
It toggles between portrait and landscape mode.