Using Supplemental Reading in Lieu of Concentrating Excessive Time on the Same Textbook

I think most instructors would love to have you in their classroom. At Neutre High School, I took a class in AP European history with a teacher who is retiring at the end of the term and who is incredibly lazy. He gave an exam which had material that was not covered in the text or in his lectures. The students were apoplectic despite a ridiculous curve. What do you think of using supplemental reading in lieu of concentrating excessive time on the same textbook? It's a wonderful idea.