A Wizard of Earthsea is also definitely not a novel, but a tale. Perhaps I can summarise the difference as follows: novels affirm the truth of the particular, tales affirm the truth of the general. If you take a novel and change all the details, you will have a different book; but if you change all the details of a tale, you will still have the same tale. Faery tales are a good example: you can rewrite Sleeping Beauty as a tale taking place in the 20th century, with chemical substances instead of spells and scientists instead of princes, and you'll end up with Sleeping Beauty. On the other hand, it is difficult to imagine Crime and Punishment taking place anywhere else than a late-nineteenth century eastern-European city.
The main concern of A Wizard of Earthsea is wisdom, and wisdom and the tale are closely linked. Wisdom is both practical and general (therefore never abstract): it is a move away from the particular life, towards a more archetypical view of life as exemplifying timeless patterns that link all human beings, and, perhaps, link human beings to everything else as well. Wisdom literature, if I may use that term, does not merely tell us about these patterns (as a philosophical or religious treatise might do), but shows us to them exemplified in a concrete life, without ever allowing the particular details to obfuscate the message.
It is clearly not the case that all fantasy is wisdom literature. The tales of Lord Dunsany are; John Crowley's Little, Big is an intricate fight between wisdom literature and the novel; The Lord of the Rings has elements of it, but only elements; our current heroic/epic fantasy has little to do with it. Very few non-fantasy books of the last century are wisdom literature - the novel reigns supreme. Perhaps the most interesting piece of wisdom literature in modern literature, if a boundary case because the fictional aspect is of relatively low importance, is Friedrich Nietzsche's Thus spake Zarathustra.
In Le Guin's A Wizard of Earthsea, we are told about pride and its price, about fear and courage, and about knowing yourself. The tale is clear, vividly delivered, and profound. Here is a quotation:
I wonder, I really and non-rhetorically do wonder, whether the tale lost its power in modernity, or whether we have merely forgotten its power.
"Tell me just this, if it is not a secret: what other great powers are there besides the light?"
"It is no secret. All power is one in source and end, I think. Years and distance, stars and candles, water and wind and wizardry, the craft in a man's hand and the wisdom in a tree's root: they all arise together. My name and yours, and the true name of the sun, or a spring of water, or an unborn child, all are syllables of the great word that is very slowly spoken by the shining of the stars. There is no other power. No other name."
Staying his knife on the carved wood, Murre asked, "What of death?"
"For a word to be spoken," Ged answered slowly, "there must be silence. Before, and after."