Peter Dickinson’s success comes from taking a radical idea, keeping it simple, and applying it to very specific situations and plots. By doing so, he is able to draw on the strengths of the traditional quest or flight story, with youthful heroes and heroines showing typical virtues of courage, resourcefulness, perseverance, and sympathy without sidetracking interest too far down a science-fiction bypath.
The main themes of the trilogy fall into psychological and sociological categories. Dickinson shows the effects at general and familial levels of fear, as well as the ways in which individuals and society deal with it: scapegoating (of witches, outsiders, and the mentally retarded); authoritarianism (reversions to patriarchal norms and feudal hierarchy); and ritual (the reemergence of a highly liturgical form of Christianity). Children are shown to have greater resilience than adults and to be much more flexible in their thinking.
At a sociological level, Dickinson depicts a society in chaos and how attempts to restore order are made. By showing how quickly a highly developed civilization disintegrates, he poses searching questions about the depth of Western norms and institutions, both morally and structurally. In his treatment, the hatred of machinery, while basically shown to be harmful, has about it a certain ambivalence. The rustic lifestyle and lack of rush are portrayed almost nostalgically at times.
Of the trilogy, Heartsease is the most carefully written and seems to have a depth that the other two books lack. The final denouement of The Weathermonger reveals the thinness of the supernatural motif in its bathos.