I have. Such books have helped me to gain a general knowledge, but have proven to be faulty on a situation by situation basis. You see, the problem with them is they make generalizations, for example, generalizations on body language. I read somewhere that crossed arms are a sign of defensiveness. My life experience showed me that it was true in some cases, but not all. Actually, the meaning behind crossed arms varies greatly from individual to individual. And that’s just one example.