Harley Hahn seems like a friendly neighbor cool dude in the college, who will show you some cool tricks with Unix, make some lame ass jokes and laugh himself and write some poems about Unix.
But he is an accomplished writer. Technical books are seldom not dry. Even when the concepts are easy to learn, sometimes you get 'bored out' of the book. In that context, the book is an accomplishment despite the fact that it has 900+ pages. It is very, very easy to read and accessible. I really feel that if the author hadn't insisted on making the chapters standalone so that they can be read in any order, that decision alone might have cut some 15% of the pages. And I am being a little pedantic about the length because it takes too damn long to finish. I think maybe it took me 10 hours or so, that too when it is light on the concepts, technically.
My intention to read this book was to make up for not having any introductory course on Unix in my bachelors yet I have to use Linux on a daily basis. My purpose is definitely fulfilled.
I think positives are well captured by the rating. Negatives, I think Harley's repeated phrase of Unix for smart people gets a little old. He also fails to truly make you realize why Unix is elegant and beautiful. Just read the first chapter of The Art of Unix and you will realize what I am talking about. Also, a little bit more technical and formal deep dive would have been appreciated maybe as optional sections. Finally, the final or the final two chapters seem a little bit rushed, if I compare them to how well and comprehensive the earlier ones are. Oh, and they could have added some real life exercise like log scraping for errors wherever applicable to make it more interesting.
Overall, I really like the book and I would recommend this book unless I find another one which is as easy to read but with maybe 50% thickness. :)