I like my Kindle DX and Larry's Kindle because I can move books onto them from other sources. Baen Publishing, for examples, has a free library with some books that I really like. They are science fiction, fantasy, alternative history, interesting stuff. I can put their books onto my DX (my husband would be very unhappy if I put those books on his Kindle). But I can't put them on my Kindle Fire. I can get free books onto it through Amazon, but they have to be free books that they offer and sometimes even when it says online that they are free, and I get an email that says $0.00 charged to me, I think I've still been charged. I have gotten some really awful books for free. I've gotten some good ones, but I stopped getting free ones for a long time because of just how awful some of them were.
I love my Kindle Fire because of the internet and email. But I really like to read on my DX.