It's the freeway or no way
Of course this is not exhaustive, however, ePub works with most reading devices. Kindle software is a free app for your phones, tablets, computers 'phablets' (Walt Disney just told me that one!) as are eBook library managers like Calibre, and you can always fall back to a PDF which is still great free software.
|Desktop / Laptop|
|Kindle Reader Software (available for mac/pc/iphone/ipad/android)||azw / mobi|
This is true in November 2012×