Shardik tells how the presence of a monstrous bear inspires a subject island people to overthrow the ruling empire. Confident that this bear is Shardik, the promised incarnation of divine power, the Ortelgans capture the capital of Bekla. They are led by Kelderek, who first discovered Shardik. While Kelderek ministers to the captive bear, the Ortelgans consolidate power throughout the empire and begin to rule harshly. Shardik suddenly escapes from Bekla. Following him into the countryside, Kelderek discovers that Ortelgans have allowed the slave trade to flourish. When Shardik perishes in the act of saving some children from a slaver, Kelderek believes that this is God's revelation: children must be cared for if society is to flourish.

Fundamentally Shardik is a novel about human misery. From the opening description of a forest fire, destruction is the constant occurrence of the novel. Shardik is the antithesis of Watership Down (1972), showing the ravaging rather than the reestablishment of community. The novel is filled with riveting scenes of death and devastation: the sack of the capital city, the slaughter of a Beklan army, Shardik's destruction of his temple, and Genshed's torture of enslaved children. Although the novel ends with Shardik's revelation about children, this commandment is only a hope rather than an accepted principle.

Thematically, the novel is a puzzle. Shardik may or may not be divinely ordained. The bear's actions in overthrowing the empire and freeing the children can be interpreted as deliberate or as accidental. If Shardik is divine power incarnate, this power is both awesome and murderous; it is responsible for the death of thousands of innocent people and allows the Ortelgans to act for ill as well as good. Insofar as they are a chosen people, the Ortelgans are unstoppable. They are also uncontrollable, using their newly acquired power to act more imperiously than the Beklan empire.

The central conflict in the novel is between the Ortelgans and the Beklans who represent intuitive and rational ways of knowing. The Ortelgans accept the divinity of Shardik on faith; they act instinctively, without thinking of consequences, trusting to providence. The Beklans determine their actions by weighing pros and cons, by taking logical steps to perceived ends. The Ortelgans lack a sense of history and aesthetic appreciation; the Beklans possess a strong sense of civic identity and cultivate civilized pleasures. Ambiguity and polarity have led reviewers to speculate about Adams's meaning. Is Shardik a historical commentary, an allegory of the coming of Christ, and of the impact of Christianity upon a pagan Roman empire? Is Shardik a contemporary tract about revived religious fundamentalism in a technological world which thinks it left the idea of faith far behind? Is Shardik a philosophical meditation upon the power that myth holds upon human imagination even in a scientific age? Is Shardik a timeless warning, the book of a new prophet who lashes a society that, despite its notable accomplishments, continues to abuse and neglect its children?