Or maybe she is just more aesthetically sensitive. Good book typography is pretty complicated thing and is done manually, so it couldn't be done adjusting stuff

Or maybe she is just more aesthetically sensitive. Good book typography is pretty complicated thing and is done manually, so it couldn't be done adjusting stuff like line height and font size in the settings of your ebook. I don't really give much attention to such things, but if you'll show your ebook reader to some typography-savvy friend of yours, he could point out quite a lot moments about "why this kind of typography sucks". Or, well, you could just take some old book with good typesetting and carefully compare it yourself to what you see on the screen of your ebook reader. Difference is pretty obvious.