This book as its title suggest is for newcomers to drools. As explained in the drools tutorial, when using drools you will change the classical development paradigm you are using going from procedurale to declarative programming. The shift is not complex to accomplish but there is a need for a onboarding set of tutorials that will help you to jump into implementing algorith/business rules wiht drools with no difficulty.
As a regular trainer of drools, I can only encourage you to do the exercices completely by yourself and try not to go the solutions directly. By doing so, the learning curve will be a little longer but so much easier at the end. By going directly to the solution, you will miss 50% of the training content.
You can find here all the materials that go with this book.