I actually really enjoyed reading this book.
I few months ago I took a Linux System Administrator course that was 8 weeks long, full of videos, interactive labs in a Linux environment, projects, etc. This book was not as deep as the college class was, but in all fairness there's really no way it could compete, especially with the lab work.
One big take away from this book for me, is that for this kind of stuff you really have to get hands on training to really learn the material. As much as I enjoyed the refresher training I received from this publication, nothing beats actually being in a *nix environment going through the commands line by line.
Again though, for a supplemental text book to go along with hands on, this book is great and does exactly what I feel its purpose is intended to be.
I would only recommend this book if you have actual *nix experience, I would not use this as first timer introduction type material. And at the same time, holding the expectation that you probably won't learn a whole lot of new stuff, because you have previous experience, but you will sharpen up skills and a lot of memories from your previous training will come back to life which is of course great reinforcement and making you more knowledgeable within *nix environments and improving your skill/ability level.
With all of that established and with that defined expectation, this book deserves a solid 4/5 for content and delivery about Unix basics.