I'm a big reader and I have a basic kindle - I love it and use it every day. The mat screen means that I can read wherever and in whatever light conditions (I have a cover with a built in light for reading in the middle of the night, which I do a lot!) I don't know if it's different over here, but I find the ebooks are usually a bit cheaper than the hard copies and a friend gave me a memory stick with about 2000 classics on too.
My personal preference is to have one tool to do one job well - kindle to read, mobile to call and text, computer to work on. Don't get me wrong I can see the apeal of tablets but I think when trying to get something to do several different, and not necessarilly complimetary jobs, something is always going to be compromised. From what I've seen of the fire and other similar tablets, it's the screen issue which causes problems with glare and isn't quite as reader friendly.
From what I've seen there's not much between them performance wise, so it's down to personal preference on looks, where they buy books from and what other tasks it'll be used for.
All that said, I wouldn't say no if I was offered any!