If you are only looking for something to read books (fiction) on, an e-ink ereader is a far better option than a tablet. Far lighter to hold & much easier on the eye when reading for extended periods. You'll only need to charge the battery on it every few weeks at most compared to every few days for a tablet. Plus they are a fair bit cheaper than tablets. Plus you won't get distracted from your book by emails or games like you would on your tablet!
If you want it to be able to do other things, then fair enough. I have both, and wouldn't dream of reading a book on my tablet when the Kindle is sitting there instead.
It's not a Kindle but the Nook Simple Touch is a bargain at £29 if you can find stock in your local Argos, Currys, John Lewis etc (it won't read books you get from Amazon without rooting it first and installing the Kindle app on it - which might not be ideal if you are a bit of a technophobe).