It's difficult to know who precisely this book is aimed at. It's relatively thin but attempts to cover an comparatively broad range of subject matter, and as a result does not develop the subject matter as well as it might. There are three principal sections. The first two cover interactive command line use and shell scripting. It's fine as far as it goes - a little dated in places but not enough not to be relvant. The real issue is a lack of depth and coverage. I can't help compare it to O'Reilly's Unix in a Nutshell which has greater depth and considerably broader scope, even if that does lack some of the absolutely introductory material this book provides.

The third section is a basic overview of various aspects of Unix system programming. However, it deals ONLY with Unix programming and assumes a prior knowledge of general C programming. As such it seems a curious fit bearing the first two sections in mind: should a book that explains how to log in to a Unix system assume a familiarity with programming? Again, the coverage is fairly shallow but here I think that serves a useful end - it is sufficient to put an area into context in a way that man pages do not. Just do not expect to walk away with significant expertise of anything on reading the appropriate chapter of this book. Like the first two sections, it is dated in places but not enough to make referring to this book counterproductive.

So, overall, is it worth buying? That depends. For an introductory Unix book I would suggest not, since there are much better books out there. The Unix system programming section is better, shallow as it is. If that is of interest then possibly it is worth picking up a copy but not at full price. There is usually a selection of used copies available at a small fraction of the new price. Picking up one of those is not a bad idea even if you only refer to it on a couple of instances: it's good enough to save time gaining a basic familiarity of the subjects covered.