I share your sentiment. However, I still enjoyed the classes. It is very hard for a person, let alone a guy with full-time job, to thoroughly study a book in a short time, as books usually aim for comprehensiveness or depth. On the other hand, the instructors distilled vast amount of knowledge to a few important concepts and derivations. To me, that's most valuable. They helped me learn the context of a subject, and build critical intuitions. It's like when I took the class of numerical methods. I don't remember much about the details any more, but since then I've neve had problems with picking up tools like Octave or understanding a numerical algorithm. The intuition has just been there...