The High King is the last of five in the Prydain chronicles, a masterpiece Fantasy work that deserves it's own genre.
Taran finally finds what he's best at, to lead others.
He rallies troops and fights the evil hordes of Arawn in the last battle. He must then decide between traveling into the west, to live forever, with his friends, or stay as king and mortal in Prydain.
The first time I read the book, in my teens, I cried at the ending, but it couldn't end in any better way.
I went on reading all Alexander's books I could find (there is an abundance),but as good as they all are, they couldn't match the Prydain Chronicles.
Read them, reread them and give them to your children!