Which ebook reader should I buy?

Waiting alone at a dark, midlands train station and typing this post to keep circulation going through my fingers and and because the light from my phone seems to be the only illumination. The battery is running low though and I don’t want to know what happens around here when the lights go off…

…if you don’t hear from me again the assume the people of Wellingborough have done for me. If someone could gather together all of my unfinished stories and give them a posthumous publication that would be great.

Assuming I make it back to civilisation eventualy, I am starting to covet an e-reader. The problem is that none of the current models seem to have established a real foothold and I’m not confident that whatever I buy won’t be defunct by next year. Anyone have any buying advice?