I have not read the later books of Earthsea properly. The first three books I read as a teen multiple times. Then five years ago I picked up Wizard of Earthsea, the first in the series. Which lead me to read the sixth book (The Other Wind) of the series. I thought I had read the fourth book (Tehanu), but I have no record of reading it.
So I am all wrong about reading this series. I have picked up the threads of the story and I think I mostly know what is going on. But if I were recommending it, I would tell you to read the series in order and not spread out by 30 years. (Although it was over 30 year spread from the start to the completion of the series.)
There are six stories here and a description of Earthsea. The stories range from 130 to 25 pages. Not unusually, I liked the longer ones more than the shorter ones. The first two and last I think were the best. Throughout the book there was an exploration of why the wizards were only celibate men. A history that shows that the founding of the school at Roke was not by only celibate men. And the final story is about a woman that comes to the school to learn to be a wizard.
The other theme of the book is why and how power is used. All of the stories concern power of one sort or another. When the magic is present to only some. And that magic gives power, there has to be some sense of how and why it should be used. Magic in Earthsea is bound by a balance. Use of magic is limited by the balance of the world around you. The stronger the magic, the more impact it has. Roke is concerned with magic, but not always with the ethics around magic. There is not a religious system in Earthsea that teaches ethics. It is the magic itself that teaches. But like many teaching, experience is how many learn. And experience can be a hard teacher.
I need to go back and try to read book four and see if I have read it and forgotten or if I have not yet read it.