I bought the book when it first came out, soon after Bruce died. I believe his wife, Linda, compiled his extensive notes (likely with the help of some unknown person.) I was very much enthralled by it. I strongly disagree that the book is just a cash grab and disjointed. It does cover a great range of martial art topics and philosophy (both of which he studied extensively) but that only shows the breadth of Bruce's knowledge and interests. Kung fu, fencing, boxing and wrestling are discussed and the value of their techniques acknowledged. Footwork, strategy, timing and mental attitude are all discussed as well. Like I said, there is a wide range of information to be found. His personal view of martial arts (physical and spiritual) is clearly defined IMO.
I especially like his definition of art - to paraphrase since my soft cover copy disintegrated decades ago: Art is the excellence of technique infused with the spirit of one's self. I think this holds for all arts, including martial.
I would not go with an audio copy of the book as there are numerous, helpful, illustrations, and for me, reading the words makes it much more personal and allows browsing and re-reading the gems of insight this book contains. To be honest, I have not read this book since I was a younger, perhaps more impressionable, man, but I suspect that reading it now would still hold my interest and get me thinking.
P.S. Bruce would criticize your use of the word "style" when referring to his art. For him, JKD transcended the limits of style in the spirit of the formless Tao.
