This is a very dense book and better used as a reference than a read-through-in-one-sitting book. There's so much information here, and most of it is helpful. In many cases, it's more accessible than sifting through loads of internet articles.
Because Spanish is so widely used, the regional slang and "normal" speech can vary widely as well, which means sometimes this book will offer helpful alternatives and sometimes it won't.
In the appendices, sometimes nouns are given without the article, and I was left wondering if they were feminine or masculine, which was annoying.
There was some mild profanity used in the book, including God's name used flippantly, which was unprofessional. (There was a chapter all about what's considered profanity in Spanish, and while I disagreed with a couple things there, the chapter was mostly helpful and the "mild profanity" I reference above was not what's in this section, but the unnecessary use of it throughout the book.)