The High King is not the strongest of Lloyd Alexander's Prydain quintet. He's building here on an established foundation, and much of the outcome in a YA adventure is foreordained. Still, for all that there's little suspense, familiar, well-loved characters are here to follow the path marked, and they've grown up a little as they've gone. Taran is wiser, Eilonwy (slightly) less flighty. Gurgi, Fflewddur, Doli, Kaw, and all the crew make their appearances, including some characters readers may have forgotten.
There are a few surprises in the book, which is more somber than its predecessors. And, if much goes as it must, at least it's well done. The ending, however, is disappointing. We all know what will happen, and why - in part because the story echoes so many other familiar tales. I wish that Alexander had worked just a little more magic here, and reached for closure in a somewhat more original way. That may be asking too much from a series that unabashedly drew from many sources, including Welsh mythology in particular.
Aside from a weak ending, the book is a fitting conclusion to the series. And, if you've read the first four books, you're going to read this one. It's not the best of the batch, but it's still good, and it'll do your heart good to know where Taran, Eilonwy, and even Hen-Wen the oracular pig have ended up.