The very first thing I would do is talk to him about it. Is he insulted, or are you? What does he think his teacher would do if he asked to change the assignment? Would he like to talk to her, or would he like you to?

If he doesn't like the books he's getting, I might treat that as an opportunity for learning self-advocacy. "Teacher, I wrote the book summary you asked me to, but the book was really boring. Can I do this one next week?"