The book itself, of course, gets a full 5 stars. Mill's work represents some of the first fundamental progress to be made on inductive logic and probabilistic reasoning and, as such, underlies much of modern scientific methodology and machine learning. He was also an excellent writer, and his prose is a pleasure to read.
However, be aware that this edition (A System of Logic: Ratiocinative and Inductive, University Press of the Pacific) is a "facsimile" of the 1891 edition, featuring incredibly small type (8pt Times, approximately) in an odd two-column layout. The text quality is poor (by normal standards), and it is quite a strain to read for extended periods. The publisher's blurb in the book claims its goal is to "make original editions of historical works available to scholars at an economical price," and that the text in this edition has been digitally enhanced. I doubt it. The text looks no better than the 1933 printing I was able to obtain from the university library. While I can see the value of having a "historical" edition, I have to believe that most scholars would prefer a critical edition that they can read without a magnifying glass.
It's very unfortunate that the only two editions available of this great work are of such poor print quality. The other edition (with the purple cover) is even worse than this one, in my opinion, and I had to return it due to cropped-off text on the left margins. I'm also not sure why a "facsimile" needs to cost 40 dollars; this is very discouraging. The text of Mill's work is in the public domain, so you would think someone could offer a good, cheap printing. Naturally, one can find the full text online, but who can read a 600-page book online? Not me.
So, all told, it's a great work by a great author. And I guess this edition is your best bet until something better comes along, although it does a disservice to a great thinker who should be more widely appreciated.