I'm currently trying to get to know the Linux console a little more after shying away from it by using various GUIs for a couple of months, so I guess I'm a beginner when it comes to Linux. I purchased this book as a general reference, based on the solid reputation of O'Reilly, and wasn't disappointed... It is basically a printed manual for all those commands you use but can't quite remember the syntax for. While endlessly typing "man" would get you a fair bit of the same information for free, the usability of a book is considerably greater :-) It's great as a desktop reference, and as you can imagine my copy has multiple bookmarks in it... It covers the "important" bits in quite a lot of detail, such as sed, awk, routing... I also bought a Perl book and together these have provided all the information I need to get acquainted with Linux. Now I just need to do it! Caveat: This is not an introductory book. If you don't have a clue what command you're looking for, this book will not always be of help (the best advice I can give there is to use Google and an expert friend - if you don't have an expert friend, there are many many mailing lists out there that tolerate such silly questions as "How do I reset the date on my computer?") -- however, Linux's logical command-naming system often means you can guess, look it up in this book, and find out what a command does *without* it damaging your system. Also, for a beginner the endless possibilities of command-line options can get really overwhelming, but they also provide the power behind Linux and so it's a great thing that this book lists them in intense detail. Not a cover-to-cover read, but definitely indispensible.
This is the best comprehensive first-line reference I've seen for Linux to date. It's most emphatically not a tutorial or a book on system administration, but when I want to know how _that_ command works, or what _this_ flag does, it's the book I pick up first. Its examples are quite good, and it's well organized.
New to Linux, and needing a general guide and introduction while extending the capabilities of my Arm based NAS unit I selected this as a good place to start. Like any guide to an operating system this is not a gripping read, but it's well structured and 'does what it says on the tin'.