I was watching this video on youtube and I would like to question what is the difference between the lessons and the Book activity. I will argue (judging by the video) that the navigation would be advantage, but lessons also have these navigation benefits as well as other resources like upload functions.
Please look at minute 10:38 as he mention that the advantage is the navigability against lessons.
I personally like lessons because I am able to extract a lot of information about it.