Well, this book does actually tells you EVERYTHING about the catalan grammar. This is both a pro and a con.
The good thing is that if you could EVER learn all rules and stuff, you would be able to master the language. The truth is, just like many grammars out there, it goes maniacally into details, things that not even Catalans themeselves know about their own language.
Moreover, I wouldn't recommend the book to people who already speak a similar language (spanish, italian, portuguese, french) since the book continuously/maniacally shows (and it's very good at it) the differences between catalan and english... this might be very confusing. It would be betterm in this case, to find a catalan grammar in your own language.