This is an excellent supplementary book to your Nihongo arsenal. It covers a suprisingly large amount of grammar, all in a well thought out description. This book covers mostly colloquial speech, which is nice for those of us who dont have access to hearing Japanese conversations very often (if at all). In-formal forms of speech are explained (along with their polite equivilant) which I loved, because unfortunatley in classes and textbooks, they concentrate almost soley on polite speech and no informal contexts. So you wont be suprised to find out the Japanese person you are talking to isn't talking like a textbook.
This book uses kanji/furigana/katakana along with romanji and then translated into english, so if you havent memorized your 3 alpahbets yet (especially the motherlode, kanji), dont fret.
I wouldnt recommend this book to fresh beginners, I think to have some understanding of it you need to have at least some basic Japanese (few months or so).
I gave it 4 out of 5 because I think this book is lacking without some kind of workbook to go along with it. With a workbook, this book could probably replace alot of textbooks.