This second book in the Chronicles of Prydain follows closely on the trail of its predecessor, The Book of Three. The writing is light, humorous, and instructive, in the sense that there are plenty of lessons here for young readers - primarily about pride. It's in no way heavy-handed, however. In fact, it's a fun adventure story that puts some surprisingly heavy decisions on the table.
Alexander drew on Welsh mythology for his Prydain, and many of the figures are at least faintly familiar from those and other legends - for example, a trio of wise women who weave, take turns being each persona, etc. Young readers are less likely to be familiar with the source material, and in any case, Alexander does a nice job turning it to his purpose.
Less successful is the pacing. Alexander rushes into the story, and ends it nearly as quickly. The characters, for all their difficult decisions, are not terribly deep. Nonetheless, the story succeeds at its main goal - as a friendly but exciting adventure that encourages its readers not just to choose the path of right, but to consider why and how it is right.