I know enough about UNIX to just get around. This book is the crutch that I use to make it seem like I know UNIX. My experience is that this book is far more often right than man pages. I see this book on about every other bookshelf at any UNIX shop I work in.(trailboss Jan 2000)
If you work with any flavors of UNIX, this book is an absolute must have. And if you do work with UNIX and you DON'T have this book, all I can say is to slowly back away from the keyboard before you hurt yourself.