I have the 3G / Wifi e-ink keyboard one. A person I know had a DX and I got to interact with it, and it was way too big to read comfortably. The keyboard one is

I have the 3G / Wifi e-ink keyboard one. A person I know had a DX and I got to interact with it, and it was way too big to read comfortably. The keyboard one is like a softcover novel where the DX is like a hardcover textbook. The small one is a lot easier to read / hold, and PDF displays pretty well (as long as the text isn't tiny... like a magazine). Most ebooks come in native mobi and epub forms anyway, so you shouldn't have trouble there.