This book starts from the very basic points on magnetism leading to the current progress in the magnetism in low-dimensional systems.
The calculations in this book are all written out in great detail. You may lie on a sofa and easily follow the calculation without using a pencil.
However, for the sake of the clearness of the explanation, a lot are omitted from this book. For example, Landau diamagnetism and Van Vleck paramagnetism, both of which are of great inportance in the physics of magnetism, are not even mentioned in this book. Also, there is virtually no microscopic explanation, such as the theory of Hubbard model, on the mechanism of itinerant ferromagnetism.
After finishing reading this book, one needs to read more advanced textbooks to understand the fundamentals of magnetism. For an introduction to the physics of magnetism, this may be a good book. However, for an introduction, there are already many good textbooks and I don't find any particular reason to choose this book as an introduction. One advantage of this book is that it has a lot of explanations on the experimental facts of the magnetism in low-dimensional systems. If you are interested in this particular topic, you may find this book useful. But, the title "Fundamentals of Magnetism" is a bit misleading for the content.