I would not say that there is no point trying to memorize a full book. It is an inefficient use of one's time, sure. However, I believe it can have some benefit

I would not say that there is no point trying to memorize a full book. It is an inefficient use of one's time, sure. However, I believe it can have some benefits. Typically, the process of trying to memorize (assuming one does not do it in the dumbest way) leads to a deeper understanding of some subtlety of the subject.