I first came across this book as recommended by my Japanese teacher as she sometimes uses it as a compliment to the lessons I take weekly. Now, although this book does cover a lot of the important base points of the Japanese language (particles, useful vocabulary etc), I do find that it doesn't really put enough time into drilling these essential grammar points in.
For example, at the beginning of each chapter, you're given a quite nicely laid out page of points on how the proceeding chapter's main grammar points will be used and the formation of it's sentences. Sounds great but it's just one page! To me, that's just not enough. My teacher puts a great deal of (I think necessary) time each week into these points as they really are the building blocks of the language and to just skim over these key points in one page doesn't give the language the respect it demands.
Aside from this, I also find it's techniques of teaching vocabulary a little rushed as well. Now I know the title is "Japanese For BUSY PEOPLE" but there are some sections that need to have time taken over. Generally, this book just lists new vocabulary in a tiny bar at the bottom of the page each time it's used in one of the book's (I'll admit, very useful) target dialogues. Vocabulary is my weak point in Japanese and I find flash cards, repetition etc essential. Just listing words without even putting a picture next to them (in MOST cases) feels like they've written out the dialogues and then just casually mentioned the vocabulary. To me, this leaves me feeling left behind and so, the rest of the book can become slightly daunting. If I didn't have my Japanese lessons to back up the material, I think I would find this book very frustrating.
All in all, Japanese is a difficult language. That point coupled with the fact that there's so many Japanese books on Amazon that can be daunting to someone starting off has led me to be very critical of this, and any other language book. None-the-less, JFBP is, for me, the perfect compliment to a night class as it serves well as a summary and I can't stress enough how much this has helped me.
Just a quick warning though: This version is the "Kana" edition which means it's written in the language's two most basic character sets; Hiragana and Katakana. This means you'll have to be able to read these sets of characters before this book will make an ounce of sense so bear that in mind! There is a "romanized" version which writes the Japanese in it's English syllables but to really progress in Japanese, I recommend learning the Kana and then using this version. It may seem daunting but it's really quite easy especially if you use an amazing book called "Remembering the Kana: Hiragana and Katakana" by James Heisig.
The bottom line is that this really is a great book but it's lack of attention to grammar and the way it teaches vocabulary unfortunately warrants taking it down a star. Still essential though and probably the best book I can imagine when used alongside a properly tutored Japanese course.