This book makes studying soooo much easier. It gives you a daily excersize to start with, to focus on, rather than sitting and feeling overwhelmed with all the things you want to study.
Very interesting exercises, they work, they keep you fit, they make your hands faster and stronger and gives you lots of resources from different techniques and styles. Then you can go deeper on your own, but it's a great start and stay focused.
The exercises are grouped in different styles, but they are techniques that you can use on any other style. For example, I play jazz, blues and surf music and I hate heavy metal, but the first exercises are grouped in this style. Still, you can use them in any other styles.