I almost completely agree with TheHumanTim.
However, if you take a look at the tutorials/topics on how to memorize books, you’ll see that depending on your strategy, you may also need to memorize the structure of the book, which are usually divided into chapters numbers so PAO, pegs, etc can help you
For example:
1. Subject X
—1.1. Group X
------1.1.1. detail X
------1.1.2. detail X
—1.2. Group X
------1.2.1 detail X
2. Subject Y
—2.1. Group Y
------2.1.1. detail Y
------2.1.2. detail Y
I recommend to search for memorizing books strategies here. Speacilly this Memorize a professional book - #2 by SilvioB that could help you.
In other words, I think haveing a PAO list (or an equivalent system) is worth and could help you in some aspects of memorizing contents of books.
You should give a look at How to remember more from books I read too. TheHumanTim gave some good tips on how to memorize books there.