Despite the title, the book starts with surprisingly simple mechanics but escalates exponentially in mental difficulty. The core concept is : the ability to play a steady jazz ride pattern (on the ride cymbal) and hi-hat chicks (on 2 & 4) while your left hand and right foot improvise freely.
The book is structured into sections that increase in rhythmic complexity: Advanced Techniques for the Modern Drummer by Jim Chapin advanced techniques for the modern drummer pdf