S H Butcher’s classic translation of Aristotle’s Poetics, with a detailed commentary and explanation.
About The Poetics (from Wikipedia):
Aristotle’s Poetics is the earliest surviving work of dramatic theory and first extant philosophical treatise to focus on literary theory. In it, Aristotle offers an account of what he calls “poetry” (a term that derives from a classical Greek term, ποιητής, that means “poet; author; maker” and in this context includes verse drama – comedy, tragedy, and the satyr play – as well as lyric poetry and epic poetry). They are similar in the fact that they are all imitations but different in the three ways that Aristotle describes:
Differences in music rhythm, harmony, meter and melody.
Difference of goodness in the characters.
Difference in how the narrative is presented: telling a story or acting it out.