[ProDigit]

The problem with large sized ebook readers is latency.
The slower CPU (which on itself is fast enough) is slowed down by slow ram, slow flash memory, and an even slower screen.

But that's what you pay for to get a near to 10x increase in battery life compared to computers or tablets!

The future for ebooks is bright though!
Certain ARM manufacturers are going to manufacture their chips with intel, at 20nm; meaning 4x lower power use, and upto 4x faster performance!
They're also working on the all-in-one system chip; so the chip has direct access to the RAM, being on the same die with it... Though those ideas are about 2-5 years off.

And I'm not even mentioning the potential breakthroughs on e-paper (one being printed on plastic instead of glass, resulting in much lighter, and thinner devices); two being the continual research to get better results on e-ink through improved drivers, and faster response times.