If a lecture is so boring, but it is given by a learned professor, should I keep on listening?

If I spend a lot of time on a lecture, but it only provides so little for us to learn, should I keep listening?

If what you have taught about is all in a little book, why should I listen to you?

Can you give me something outside of that little book?

I am so disappointed by the lectures given by those professors in this famous university in China. This school is too proud to develop. Remeber my word!