Until the Celebration, the final book in Zilpha Keatley Snyder's "Greensky" science fiction trilogy, is the least successful of the three. Below the Root, the first book of the trilogy, presented an imaginative and convincing future society with a strong focus on three Kindar young people…. And All Between, the second volume, retold the story of the first book from the viewpoint of Teera, the Erdling girl—an interesting innovation, but one that was not entirely successful. Until the Celebration founders in sociological issues in spite of Snyder's effort to provide suspense, and probably only the stubborn, the curious … will persevere to the end to learn the fate of the main characters.

Science fiction is frequently described as "a literature of ideas" and Snyder's trilogy is not deficient in this regard. Her major themes of peace, brotherhood, and non-violence are indeed admirable, but she seriously undermines their effectiveness...