I've just started with this book and am about 1/3 through but I can state already that it is very fun and the progression in difficulty is gradual and quite manageable. The exercises do a great job of balancing left and right, and together with the displacements, this is more of a "brain workout" than a physical regime. Once you start to add foot ostinati, or for example, add the bass drum to all accents or even orchestrate the ideas around the kit, this can start to sound very musical. But I think these are best used as part of a warm-up routine to get your hands and brain limbered up. Thanks to Steve Gadd for this groovy little rudiment book!