I'm pleased that this book is as complete as it claims to be. Between the two volumes, the readers meets with every aspect of Aristotle's thought, including almost one hundred pages of fragments testimonies.
Unfortunately, I also have several complaints...
a) most of these translations are old - early 20th century old - and this doesn't always make it very easy to read them; they are, if you will, 'classic' translations, but I would have preferred to see Oxford hire a new team of translators to assemble and Aristotle fit for the new century
b) there is very, very little commentary - admittedly, here I compare the complete works of Aristotle to the complete works of Plato, published by Hackett. In Hackett's Plato, there are occasional footnotes to aid the reader's understanding of difficult passages. The Oxford Aristotle only notes paragraphs that were excised in the original translations, and, very, very occasional (10-20 times in the entire library) provides more substantial notes. There aren't even endnotes!
c) there are no introductions to give context to the works - again, I compare with Hackett's Plato. It would have been nice to hear the story behind works of disputed authorship, rather than simply placing a * or ** next to the title of the dialogue. It would also serve to consider how each work relates to the rest of Aristotle's corpus
d) the fragments are poorly arranged. I can see how certain fragments might not specifically reference a certain work, but the editors already arrange them according to the works they supposedly reference - what they don't do is formally divide them as such. Instead, they are placed into general categories.
In summary, what I received from my 8-9 months of Oxford's Aristotle was an incomplete experience. I had hoped to see the best scholarship that money could buy, and instead I met with Jonathan Barne's 'hands-off' tendencies. I respect the idealism of leaving a work to speak for himself, but I also deeply appreciate the guidance of those who have read the Philosopher before me.
Would I buy these books again? Likely, no, I would instead go through the hassle of assembling all of Aristotle's work in smaller collections, finding editions of different works that feature introductions, footnotes and newer translations.