This is the best hip-hop book I've had the pleasure of reading, mainly because it focuses purely on the musical side and not on the more academic stuff, as another reviewer pointed out. It's almost all in the words of the MCs and it is edited in a way so that there is no filler, just tons and tons of inside techniques and stories from the actual artists.
There is a huge range of MCs interviewed and it's all organized so that you get the most useful and most interesting quotes from the MCs in the right places. I was particularly pleased to see so many of the legends present, like Big Daddy Kane and A Tribe Called Quest, and it's put me onto a lot of the dope underground groups like Jedi Mind Tricks and Aesop Rock.
I'd recommend this book to all hip-hop fans, along with the books Check the Technique and There's a God on the Mic - hopefully there will be more hip-hop books like this in the future.