Personally speaking, I much prefer to read on a dedicated e-reader, with a nice e-ink technology display. It's a much better experience than reading on a back lit computer display - be it desktop, laptop or tablet.
However, if you're only going to read for a short period of time, if you want to read something that uses a lot of images, or if you just don't have your e-reader to hand, you can certainly use a tablet for reading.
I think that the smaller 7" tablets are better for this, purely because of their small size and low weight.
Here's a list of some of the best tablets for reading for your perusal: