Frankly, I bought this book because I was interested in learning more about techno/trance DJs, and was initially disappointed by the relative dearth of discussion of current trends (a discussion of these comes only in the last quarter of this book). However, my disappointment turned into appreciation as I realized this book truly is a history of the DJ, from way back in the early 1900s to today. This history offers a vast amount of information about who the first DJ pioneers were, and it is divided up into sections on the first radio DJs, northern soul DJs, reggae, disco, rap, and--finally--techno.
The authors point out that they're not doing any academic, high-fallutin' theoretical study of the DJ, but I think they took this anti-academicism too far. The DJ is a fascinating figure because s/he challenges so many of Western culture's ideas about what constitutes "music" and what constitutes "artistry." This book could have been much enriched by delving into the ways the DJ changes how we think about music.
As it is, the history in this study is admirably exhaustive; but because it doesn't connect this history to a larger history of music and aesthetics, it sometimes becomes just exhausting.