I just finished reading Ursula K. LeGuin's The Farthest Shore, which I last read when I was in fifth grade, riding the bus to elementary school. (We lived on a military base and it was a long commute each way each day.)
I didn't remember much of it before I started, other than -- as a kid -- it didn't really speak to me. I had a professor in college who advised rereading books in different stages in life, as they'll mean different things to you. He was speaking specifically about Beowulf, but it's apt here as well.
This is Ged's final adventure, although not his final book, since LeGuin started writing Earthsea books again 18 years after this one came out. She was only in her early 40s when this was published in 1972, but death and aging was clearly on her mind, along with the concept of passing the torch on to younger people.
It's a much less optimistic book than even the Tombs of Atuan, which was fairly bleak. In her afterword, LeGuin talks about seeing all of the idealism of the 1960s be replaced by cynicism, greed and drug abuse. One of the islands in this book is shockingly bleak and the overall threat facing the world in this book is pretty grim. Lots of authors have done the "magic is going away" plot, but none as well or as spookily as LeGuin, for my money.
I've never read the last three Earthsea books, although I gather they're not the romp people wanting them to be A Wizard of Earthsea 2 wanted them to be. Looking forward to them, although I suspect they'll be at least as contemplative is this one.
I do think this book would be a good pick-up for DMs, including the afterword, where LeGuin talks about dragons. She does a much better job of talking about the overlap between magic and dragons than WotC (who were clearly at least somewhat inspired by her ideas with making Draconic the language of magic) ever have.