The Kindle supports different formats. So, you don't have to buy Amazon books to read; it will accept .pdf and .mobi and a few other types. Plus you can use a converter (I use Calibre) to get other formats (like ePub) into the right format.
If you are going to the effort of maintaining open systems, I can't see why the occasional file conversion would be too much of an issue.
I wouldn't recommend the Fire, though, because it is much more difficult to work around that way. I doubt I'll buy another one.
I'm reading In Pursuit of Pennants: Baseball Operations from Deadball to Moneyball, by Mark Armour and Daniel Levitt. It's about the evolution of the baseball front office over time. They are the same ones who did the Top 25 GMs list I was posting a couple months ago.
Also, Mecca: The Sacred City by Ziauddin Sardar, about the history of Mecca and how it has always been a place of pilgrimage and controversy even prior to Muhammad and Islam.