Wow! Great responses! Thank you All very much!
My mom is very non-tech, doesn't even have email or go to the Internet (the only exception is Skype to talk to friends/relatives abroad), so whether it has other apps or not is not very important. However a good screen/contrast is really crucial as all of us have rather bad eyes. I have android tablet, and screen is somewhat hard to read for long time.
I will stop by Best Buy to see if they can demonstrate some (didn't even think about it since I usually buy off Amazon). But sounds like Kindle Touch or Nook (haven't even heard about this one) will be my pick.