I was blessed with the gift of a Kindle DX recently. Hats off to Amazon; I think they have clearly set the benchmarok for e-book readers. The unit is thin and light. The screen is _amazingly_ sharp and easy to read. It holds about a gazillion books (see Amazon site for details) and book download is automatic, via cell-phone technology. No charge for airtime, either.
The interface is intuitive, but it comes with a built-in manual anyway. Also comes with a dictionary.
I find it as easy to read as a book, and nearly as handy to carry. It won't fit in some places where a paperback would fit, but overall it is thin and light enough - even easier to carry than a netbook.
Font size is adjustable - great for older readers or bad light. You can rotate the Kindle and it shifts the display, too.
It charges via standard USB, so you can share charging bits with iPhones and many other devices.
No doubt someday someone will develop a better e-book reader - it may be Amazon, or not - but the Kindle DX is the benchmark today. Why, it's even better than an iPhone!