"The reader who has read the book but cannot do the exercises has learned nothing." -- J.J. Sakurai A lot of books from my school had exercises you could not s

"The reader who has read the book but cannot do the exercises has learned nothing." -- J.J. Sakurai A lot of books from my school had exercises you could not solve if your only knowledge about the subject was the previous chapter(s). So for those who could be bothered (most efficient technique is not doing reading or exercises at all but somehow getting a good grade) there were times one would come up with an insight or read further ahead / another reference and discover a new connection. Either way made for deeper learning.