Utopia presents an interesting and relatively unique case of narrative tone: More himself is the narrator, yet this is a work of fiction. More removes the barrier between author and narrator that exists in many other fictional works, simultaneously allowing himself to own the political assertions of his work and pass them off as mere fancy. Given that More served under a king that often killed people for opposing him, the radical political ideas espoused in Utopia likely required that protective barrier of a fictional medium. Additionally, removing the barrier between reality and fiction—between the author and the characters—further validates the dream of Utopia, bringing political change and social upheaval (at least, the kind that More desires) closer to the real world.
It is also important to note that Utopia was originally written in Latin. As a consequence, the tone of the novel is partially mediated by the translator. Depending on how the translator interprets certain passages, narrative tone may differ between translations: for example, certain translators may choose to imbue a passage with more humor than others. When reading a work of fiction in translation, it can be helpful to read several different interpretations of the same passage; and though these may vary in tone, the sum total of the passages will likely provide a more accurate, holistic picture of the author's original meaning.