From How to Read a Book

On agreeing or disagreeing with an author:

"The first thing a reader can say is that he understands or that he does not. In fact, he must say he understands, in order to say more. If he does not understand, he should keep his peace and go back to work on the book."

While I do understand that poorly written books can be rather difficult to understand, I think we should all take Mr. Adler and Mr. Van Doren's advice and seek to understand a book (or a person, for that matter) before pronouncing a judgement on it!