I read this quote, the title of this post, long long ago. This is very true. For better learning, it is essential that a teacher starts with the bare minimum knowledge and then gradually builds upon it. If you, as a teacher, try to cover all possible things when teaching, you are just confusing the learner.
This incremental way of teaching is not easy with books. Books are meant to be comprehensive and often are. Though there are techniques to learn incrementally from books (like skim reading first) but probalby not every student/learner knows how to apply these techniques. So few people learn confidently from books.
The fact that really good books are not always available for every subject and really good teachers are also in short supply makes learning a difficult thing in many situations.
Fortunately Internet video solves this problem to great extent. It is possible to start with minimum information in your first lecture and then build upon it in the next one. Khan Academy is one big example. Inspired from this mega project delivered by an individual, there will be many collections of video lectures on every possible subject in the future.
Let us get started.