I kept pointing out that each previous book was missing a certain "something" that kept them from five stars. Whatever that something is, The High King has it.
I'm afraid I haven't the time for a full review, but man does the series go out with a bang. I didn't know a Newbury Winner could be so violent. Alexander does not hesitate to kill off characters we love or to make the tasks set for our heroes really and truly feel impossible. It's a big, sweeping, melancholy, and suspenseful ending that pulls together any and all loose points that were flapping around. Also, for the first time we have sections of the book that move from Taran's point of view, which makes things seem all the bigger.
Nonetheless, it is still, at the end, Taran's story, and I wish I'd finished it in private, because I had to fight back tears.