Yes, in bright light tablets are harder to deal with....a real e-reader is best...
But the kindle apps makes it possible to read indoors on just about any device.
I have some screen shots from my mini and google nexus 7 below. There are two for the mini and just one for the nexus. The mini, with the smallest font, is too hard to read but if you soon the font two or three numbs is is fine. On the nexus, I can read it just fine on the smallest font, but the two apps are different so I don't attach any significant to what is programmed in for the smallest font. In either case, you do get more info on the screen at a readable font size. Of course, your eyes may be different than my so ymmv.