On my laptop, I'm currently running Ubuntu 12.04 Beta 2, which works great. But sometimes I just want to lie in the couch watching a movie or reading an e-book. At times like that, the power consumption of a modern desktop is a bit of a pain in the bum (about one and a half hour on a full battery).
I know a tablet or an e-book reader would be probably the perfect solution for this, but they usually cost (rather a lot) of money.
Is there a simple environment I can install (or run from USB/CD, don't care much) which doesn't use so much power, and allows me to simply read an e-book and (optionally) watch a movie? I don't need any fancy effects and features or anything, I just want a long battery life.