I think one of the most important factors in choosing a macrame book is the actual patterns. Make sure to look through the patterns first and see if there are actually ones in there that you want to make.
I'm a knitting, and I have a rule for myself about pattern books: there has to either be 5 patterns I want to make or some really, really useful information. If not, I don't buy the book.
It's easy to amass a collection of craft books you might never use. So I suggest being discerning with your purchases from the very beginning.