I have the Kindle app on my iPad, which would be suitable for photography. The Kindle itself, which my girlfriend has, would be no good for pictures. They would have to be free for me to even try, and then I'd be pretty dissapointed.
I'm a huge kindle supporter for books, I love reading that way. But I'm also happy that photography can (I hope) remain primarily a printed book format. Photography and books go hand in hand, so I'm hoping it gets easier for new photographers to get printed, even when the sale of paperbacks decline.