In the second paragraph, what is the idea the author is trying to convey about the book, using descriptors like "not textbooks," "impressionistic," and "introductions"?

The correct answer for this question is this one: "C. That the books are less expensive and more useful"

These are the following choices:

A. That anyone can misinterpret the meaning of the books

B. That anyone can understand and enjoy the books

C. That the books are less expensive and more useful

D. That the books are less frivolous and more academic