This is not "UNIX for Dummies" - it's more "UNIX for very smart people who understand something about programming generally, not necessarily C, although that would help, and are capable of following intricate reasoning from a minimal presentation, and most of all, who are sufficiently taken by the design of the UNIX operating system to read through a detailed tour of its working parts".
I am not a tremendously smart person, I understand something about programming, but not a great deal, and I'm pretty good at following a sequence of logical steps, and most of all, I'm curious about things like how UNIX fits together. Having read this book, I won't say that I understand UNIX, but I certainly have a much better overview of what pieces are required to make something like this work, and how they get put together in this case. I suspect that if I take this knowledge off into the world and return to this book in a year or two, I'll be in a position to get a bit further into the overview; it seems like a book that rewards readers at many levels of initial understanding.
The writing is not prose to savor, but it is certainly effective. The authors do not try to impress with their style, and they don't, but the explanations are clear and lucid and the overall structure is sound and well-motivated, developing from the kernel outward through process and memory management to filesystems and I/O, and finally out to the network before wrapping up with the startup procedure. There is a logical flow from one section to the next, and the structure as a whole has a coherence that technical writing often lacks. ( )