Any android phone has a number of open-source book reader platforms.
They all can be activated to have a 3g(etc) connection (at a monthly service charge), or operate perfectly fine unactivated (as in, zero service cost) from wifi connections (except to call you have to only use skype/tango/etc).
All ebooks available from amazon/kindle etc are available free to download from the right torrent sites (the best ones always being private sites). You can read them, and delete them. I see no difference from this and visiting a library to check them out, other than the electronic method involves a lot lower cost overhead and environmental impact (paper being made, books being printed, shipped, driving to library to check out, driving back to return, etc.)
Android has ebook readers and file format converters that can take any format of ebook/pdf/doc/etc etc, and convert it into a format that looks, lays-out, and reads perfectly on an android device.
Other than my stack of text-book engineering resources, I'm pretty much paper-free on my book collections now, and always have them all with me with no additional bulk to carry than my phone (which I normally have with me). When I recently moved to California, I donated many many boxes of books to goodwill, as I know I can simply have any title I had owned on my phone for 5minutes of hassle to download it at no cost, and I've come to much prefer reading in the dark from my back-lit phone's screen (turned down to be pleasantly dim so it's not taxing on my eyes). Reading this way in the dark feel much more immersive and enjoyable to me than reading with a lamp shining on paper, and with the need to hold a bulky flexy book open and turn pages etc.
