Aristotle's poetics is a much needed antidote to the opinions on Fine Art expressed by Plato in the Republic. I would suggest reading Poetics within a year of first exposure to the Republic.
I had already read Nichomachean Ethics. I agreed with most of what Aristotle said there but I was a little bored with N.E. It seemed mostly common sense (I say "common sense" in the common and common sense sense of "common sense"). Perhaps Aristotle played a large part in shaping the typical contemporary common sense everyday everyman ethical stance. In any case, I did not find the ideas particularly novel.
Poetics presented me with new ideas or rather old ideas that I had not yet been directly exposed to. The most important among these new old ideas is the idea that the arts complete and perfect the work of nature. However, art works with and toward the same end as Nature. Butcher does a very good job of making the nuances of this idea clear.
Butcher's chapters are very helpful in understanding Poetics and its new old ideas. Butcher contrasts Aristotle with Plato in a very understandable and indepth fashion. Butcher addresses the historical context and Greek mind in a sober fashion.
There is little hope that I will get around to reading Poetics in Greek in this life time. Nevertheless, there may be some value both aesthetic and instructive in having the original Greek immediately present so i will not say that the Greek is completely superfulous to those who don't know Greek. The Text is presented with Greek on the left and English on the right. The eleven chapters of commentary are in English only of course.
If you are interested in Aristotle's POETICS, this is the edition to own. You get a nice introduction, the full text of the poetics in Greek and English, and then a ton of commentary (300 pages), all of which is well organized for easy and selective digestion. A superb edition.