Like many developing writers, including such masters as William Shakespeare, John Milton, and Alexander Pope as well as more recent storytellers such as Jack London, Clement seems to have become gloomy in his later career. This novel is based on profound caution with regard to advancing scientific knowledge, a theme he toyed with in his earlier Mesklinite novels, Mission of Gravity (1954) and Star Light (1971), which discussed an energy crisis for civilizations. In a much later novel, Fossil (1993), Clement extends his speculative gloominess to question again—or at least to play with—the limitations on science itself. These explorations of the limits governing what he is most interested in, such as science and epistemology, make Clement’s writing very serious, penetrating the veneer of the adolescent plots.

The nature of Bones and the entire Observer species, as a kind of visiting angel group looking over the adolescent scientists of Earth, represents one of Clement’s most successful and representative creations. His science fiction especially has always dealt with matters of how humans communicate and share knowledge. In a concrete and fascinating sense, the Observers are pure scientists who are not confused by talking because they share knowledge by direct contact; this contact is the closest they get to sex, considering that the species reproduces by parthenogenesis. On all these matters, Clement’s tone is ironic, a little gloomy, and wonderfully suggestive, making this a powerful novel.