I listen to a lot of audiobooks, read a lot of library books and e-books, still somehow never have enough room on my bookshelves.
I hit a couple images that I recall from Dad reading it to us, but I suspect I only reread the first two as a teen. My memory isn't that bad.
Our teen protagonist of the book is the heir to a prestigious island princedom who comes to the Isle of Roke for help. The magic is vanishing from the world, and he needs the help of Arch-Mage Sparrowhawk to figure out what's gone wrong. Prince Arren then sidekicks and plays observer to Ged for the rest of the story, and has an adorable crush on his mentor throughout.
Again the point of view shift works incredibly well. Ged gets a few short scenes of his own thoughts (most of which are about wanting to see Tenar, which is really sweet), but he really did turn into a sea-going Gandalf somewhere in the middle there. He's remote, versatile, wrapped up power and magical theory (mostly Taoist), with sudden flashes of humour and warmth. There's a beautiful line about how sudden and genuinely sweet his smile is. Though I would be very interested in a book from his point of view now since I love cranky-old-person narration, he's gotten a bit esoteric for what was essentially a young adult book. A lot of the book is about how to be a good leader, both as described and as modelled by Ged, Arran (whose favourite saga hero is his favourite because he could have taken over the world, but chose not to), and a couple dragons. The Taoism gets a big didactic at times.
So much of the first book wraps back around in this story, which marks the end of Ged's magical career as the first marked the beginning. He himself reflects that this will be what he's known for, his final great quest and its almost incidental conclusion of his life's work (which showed up as sub plots of the previous two books). He spent his life learning so that he could teach Arran. He also spent his life learning so that when someone else copied his first magical mistake and then ran with it, Ged could find and fix the problem before it literally sucked all the joy out of the world. We learn what a difference being a good man a heart made to the conclusion of the first story (and how Ged's temper still causes some pretty huge problems.)
I don't know my high fantasy history well enough to know if this was the first time the "magic is disappearing" plot was showed up (I've certainly run into it many times in later books), but rarely have I seen it so well done. The depression, amnesia and onset of barbarity in the affected regions is as horrifying to the reader as it is to Arran. There are a few comedy bits of people complaining about kids these days, but mostly it's madness, forgetting and death. The descriptions of sailing to the edges of the world as our hero falls deeper and deeper in the grip of this power are absolutely hair raising, and again Le Guin's control of language shines.
Though this book again has no female protagonists, it's actually trying a lot harder than the first two to add non-evil women of power to Earthsea. Aside from the mention of Tenar, we learn that Yarrow is one of seven people Ged trusts with his name, and the most powerful wizards we meet are both women (though currently powerless because of the plot). The progenitor of the dragons pointedly does not have a known gender. The saga hero Ged sees the most of himself in seems to be a female one.