If you want it to act as a phone as well, the best eReader is the iPhone. If you don't, it's the iPod touch.
Everything sold as an eReader has two fatal flaws. First, they're all way too big, in order to have a page size big enough that they can pretend they're like paper books. An eReader should fit in a shirt pocket.
Second, e-Ink displays are horrible. They're grey-on-grey text, and the half second flash and delay on page turning is terribly distracting. LCD is the only way to go at present.
(Yes, I actually do read on my iPhone; I've read over thirty books on it so far this year.)