i've never really read any of them but i do see posts about which books are good on occation.
from what i've gathered, those books really don't offer any new info and that they are all pretty much the same. when i new book comes out, it's the same as the old one with maybe some new insite on different topics.
like sus is sus. it will never change and it will always be used in the same way.
so if you really want to buy something, i'd just find the most recent publication, flip through it to make sure it has what you're looking for, and buy it. . . for when you're sitting on your thrown