[Power of Three] is inventive, exciting and immensely pictorial. These words, used to praise, could however be the basis of a criticism of the book. It appears, on reading the book, that the author sees every scene as in a film, and she transfers the image on to the written page most vividly and successfully. The trouble arises when the action becomes peopled with too many characters, and in order to paint them in she has to litter the book with proper names, Gair, Ayna, Ceri, Garholt, Dorig, Otmounders, Adara, Gest etc, etc, sometimes as many as forty or fifty to a page, and so the narrative becomes stilted and disjointed as the words intrude on the wonderful story she weaves. Oh, for the film of the book, when the creatures of the marsh would rise in the mist, when the Giants would make their surprising entrance, and when the dwellers on the Moor could be seen with their beautifully worked golden collars and all the other fascinating inventions of Diana Wynne Jones.
Eileen A. Archer, in her review of "Power of Three," in Book Window (© 1978 S.C.B.A. and contributors), Vol. 5, No. 2, Spring, 1978, p. 31.