Before reading this book, I had very little knowledge regarding the Unix side of my Mac but now I know how to wield the Terminal application with ease and confidence. It teaches you how to use the command line in a way that not only allows you to read through it like a step-by-step tutorial, but also in a way that allows you to jump about the book if you ever need to learn specific topics immediately. It's extremely detailed and informative, considering it is a book for total Unix beginners, and it also gives you information on how to continue learning about Unix as well as how to begin learning things such as shell scripts and programming languages, such as Perl, Python, Ruby, C and C++.
All in all, this is an amazing book that you will not regret purchasing. If you need somewhere to start learning about Mac OS X's Unix underpinnings, and how it can help you, look no further; you have found the perfect book.