The Castle of Llyr applies Lloyd Alexander's now-familiar formula, with all characters playing their usual roles - Taran, Fflewdur, and Gurgi all play large parts, and Prince Gwydion comes in. Only Eilonwy, due to the nature of the plot, is largely absent.
This is not to say that the book is not amusing. It is; it's a nice continuation of the series. However, there's little new about it. Happily, that means the usual humor, the usual positive morals and character-building decisions. Taran is growing up, and this time, some of the decisions are more personal than before.
An amusing continuation of the Prydain series. If you've read the previous books, you should read this. If you haven't, you should.