I took lots of learnings from this book. Command promt is an essential tool for linux users. Personally, I like Mark Sobell's book. It is easy to unerstand them and makes light introduction to heavy topics.
I bought this book so that I could understand general Linux commands and structuring, and it has shown me a good and useful range. This book can be used as a Linux reference or admin book, but it is missing certain sections that would be rather useful.
The first problem that arises is how to add a new user on a Linux machine. This book tells you nothing on it and just leaves you wondering. I was also interested in the ssl connection configuration specifics so that we use secure connections when talking to remote Linux machine. This too was mentioned, but nothing more.
Luckily I also bought the Osborne Linux Complete Reference 6th Edition, which told me how to do the above commands.
But in general this is a well laid out book to teach you the fundamentals and higher levels of shell script, you might need a book like the Osborne one to accompany it, for more of a technical view.