"Zhu Zi's Annotations" was a thick volume comprising Zhu Xi's commentaries to the Four Books, namely, "University", "Higher Education", "The Analects", "Meng Zi", as well as "The Five Classics".
Because the later generations respected Zhu Xi, they changed the title from "Commentaries on the Four Books" to "Zhu Zi's Annotations". How could a book be that expensive, however important it might be? Besides, it was just a reference book.
Mu Yangling was not very willing for her brother to buy this book. With this book, it was much easier to interpret the Four Books, but students would then not use their brains to think on their own. What they learned would also be more superficial.
However, she was unwilling to disadvantage her younger brother when everyone had them.
