German philosopher, mathematician and man of affairs (i.e. businessman), Gottfried Wilhelm Leibniz always said that he found no book so bad that he could get nothing from it. He was referring to serious works of non-fiction and meant that he could glean a few bits of worthwhile material from any book he read. There is a more powerful way to think about bad books. The fact that they are obviously wrong helps you to clarify your own thinking. (Perhaps Leibniz had this in mind as well.) You can view your own notions in the light of the wrong ideas in the bad book, make comparisons, and work out arguments to knock down what you are reading. I make a habit of reading books (not necessarily bad ones!) that present views opposed to my own.