Beside the Bible, perhaps no Western literary work has inspired so much art and philosophical debate as Ovid's Metamorphoses. Really the only monolithic attempt to bridge the gap between Greek and Roman mythology, the epic poem begins with Creation and procedes all the way to Ovid's time, chronicling the battles between gods, the adventures of Perseus, the history of the centaurs, and most other stories connected to Greco-Roman mythology. Everyone from Dante to Italo Calvino have drawn from Ovid's masterpiece, helping disseminate knowledge of Classical culture throughout the West, so that most people have some idea of the stories even if they don't realize their source.
At the outset Ovid reveals his preoccupation with change. Not only one of the earliest examples of synthetic art (borrowing from existing sources to create something new), Metamorphoses is also one of the first and best conceptual literary pieces (organizing the work around an idea rather than a single narrative). In many ways it's the original modern novel, far more than Homer's works because it makes no pretense of historicity or deep religious significance. As a social document those elements are there, but Ovid is concerned primarily with making great art, and borrows freely from tradition to accomplish that end.
In Ovid, objects turn into people, people into objects, old ideas into new ones, and eras are formed and dissipate, always transforming, always become something other than they are, yet somehow also retaining what it is that made them in the first place. But though he never draws attention to this explicitly, the poet's greatest acheivement is the demonstration of the metamorphosis of Greek to Roman culture, the way civilization adapts to keep itself alive. Even more compelling, Ovid's own work has adopted the same purpose, retaining for successive generations that which preceded them and thus enriching immeasurably our cultural heritage.
If this sounds far too cerebral and important to be interesting, don't forget that Ovid was making art, not cultural history or philosophical commentary. He was a poet, and the beauty of his language comes through even in translation, illuminating and elevating the universality of his themes. These are first and foremost great stories, narrative poems that, even if their explanations for the nature of existence aren't exactly right, nevertheless retain the truth of human endeavor and encounter. Ovid elevates both our minds and our aesthetic selves with the music of life, its darkness and its even more blinding light.
Like all great art, Metamorphoses lifts our consiousness out of the quotidian mundanity of our lives to view the completeness of existence, to see that even our prosaic lives have meaning beyond ourselves, even if that meaning is itself a metaphor. Divinity as we know it is not as capricious as Ovid understood it to be, but humans are, and nature, and the flux we find ourselves continually a part of requires some explanation outside our individual experience. If Ovid's explanation falls short, it isn't because his art does; and if we don't understand it, it isn't for lack of clarity on his part. Because it is so plain and so true, Metamorphoses is still transforming the world we know, even as it helped establish it.