Ok, I do like gadgets I can hack or play with. But I can't justify what it costs on that basis.
I was reading free ebooks, fanfiction etc. but at a limited rate. An e-reader lets me read more than I would otherwise.
I do like the compactness of digital files. Some people like physical books; I like my library on an SD card. All ~500 Mb of it

. Seriously though, I like having less "stuff" lying around. I liked to think it would be more efficient than chopping down trees... _economically_ thats true, but I'm not going to claim it's greener without running the numbers.
I also liked the idea of downloading the various stories I'd read over the years. (I was surprised to find how many of them had been Baen free samples).
I didn't think it'd be more convenient (whether I compared it to a netbook or a physical book). But it _is_ more convenient to read a 'slate in bed; you can lie on your side and not worry about keeping the pages apart. (I wonder if that's true of an iPad...

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Unfortunately I can't remember whether I thought of this last one beforehand. But I now consider physical books inferior - because they don't have a clock that reminds me exactly how long I've stayed up reading. The e-reader also gives me a slightly better grasp of page numbers... maybe that's just from when I have to resort to the "go to page #" feature, but it also doesn't hurt that FBReader gives me a fixed 1 page = 2K of text.