If you're a graffwriter it's very important you see this at least once, which doesn't mean you should buy it. If you're a writer and you've adopted a sort of scholastic approach to learning style (ie observing style in photos and trying to sketch what you see to learn), then read this:
If you've already mastered the basics (ie letter proportions, basic connections, simple letters, blockbusters) and you're counting on this book to teach you some new tricks, don't.
All this media hype about the bible of graffiti has influenced a lot of people to overestimate this book. Let us not forget that this book is only what the photographers saw. These guys were not writers. Many crews which contributed to the evolution of style (fba, tc5, tds) are not documented. Books can only reflect the writer's quality but not quantity of pieces done. So who was king where and when is another question. Where are the real style burners in the book??!! They're not there.
Well that's up to you to look for them, if you're a true writer, document yourself, dig for those gems, this culture is underground, and there are many wack pieces in this book.
Now don't get me wrong, it still is essential to have seen it at least once to understand what old skool is. But just get it from a friend, or check it out at the bookshop. What you really should be looking out for though is old issues of tight magazine, and old underground graff zines having new york specials, there are a lot, and especially in european magz.
And if you're new to this culture, then this book won't bring you the initial spark to start your career in writing. You're better off watching Style Wars by the same author, that is worth your money at 200%, trust me. This is it ! This is it !