The book was extremely helpful for me. It filled many tiny gaps that I had. I've been with Linux for more than 10 years so far and I am not an every-day user of it. So, many things that I could learn by practice are missed due to lack of usual practice.
For people that are just starting with Linux, I think this book will be also very useful but not as useful as it was to me. Beginners reading this book will find it very useful, but they will still have gaps that they should try to bridge with more practice and further reading of books, tutorials and other sources.
If I am going to give a Linux course one day, I think I will use this book as a resource because it is well-organized. However, the material inside this book will need far more than 5 days to grasp.