"Well- by the way you've described it, you can either have books you want that are a bit too difficult for you to read comfortably--" which will frustrate you and make you hate them for being too hard, he thinks "--or the simple children's ones that you can read." And you'll resent them for being condescending.

He tucks the book under his arm, out of habit mostly. "Eponine, I'm not trying to be rude, but if you can only read a small amount, you're not going to get better unless you practise with the easy ones. Even if it feels a little bit insulting, I know you're not a child."