I EDC the Nook color and it gets great battery life. I store several good survival texts, tons of bushcraft FAQ/s word docs important data (copies of birth certs, drivers license, sevral gigs of pic. Plus my regular entertainment library.

I've charged it from cig lighters, small portable solar charger (slow but it works).

Like someone said I wouldn't rely as the only source. Should back up with paper books. but for EDC it's pretty handy