This book is for student, and, in a way, it is a book by students. The most important tool I've brought to the writing bench is my teaching experience. In front of a live audience, a teacher can discern, often by simply monitoring facial expressions, if a particular presentation is working. Feedback from students helps an instructor learn when an example or analogy can clarify a point and when it can muddle the point, when details can support the development of a concept and when they can obscure the concept. Sensitive teachers also recognize the frustration of students who are stranded between two plateaus in their understanding, not having been given enough detail to completely grasp a concept.