This is the same model of iPad that I have. I have used it to read several psychology and CS textbooks and hundreds of papers in those fields and philosophy and neuroscience. For size, this has been satisfactory for me as a middle-aged person with good uncorrected eyesight.

My wife has an old iPad mini (no idea what year/gen), which I have read some technical documents on. That was sufficient as well, though not quite as good as the larger iPad.

I've never used the larger sized iPad models, so I can't really compare.