I am considering a Kindle Fire, there is a review on Project Gutenberg suggesting it is needlessly (or intentionally) more complex to sideload free works on to a Fire. In a comment to an answer on If I buy a Kindle Paperwhite do I have to get books from Amazon? a link to this article suggests it is really not that difficult.
Is the Kindle Fire more difficult to sideload to?
The Kindle Fire is not difficult to sideload to--at any rate, the 1st generation version that I have is trivially easy: just plug the Fire into the computer with a micro USB cable, it shows up as a drive, and drag .mobi files into the relevant folder on the Fire. Easy!
The Kindle devices do not support the EPUB format. They require you to use the Amazon Format. There are converters that allow to convert to the Amazon format. So this makes side loading harder.
On the Fire, as you have the chance to install Android apps, you can install an Android ebook reader app with EPUB support.
