An essay in biography, Rollyson argues, is an effort to comprehend a life that is inherently incomplete and subject to revision. Many of the facts about a biographical subject's life that are blandly presented in reference books have been discovered by biographers at great cost to their reputations. With the history of biography as a censored genre in mind, he encourages readers of biography to look critically at the biographies they read-no matter whether those biographies are book-length narratives or short encyclopedia entries.

Many of the pairings in Essays in Biography are meant to evoke Plutarch's presentation of "parallel lives." The biographical essay, Rollyson concludes, is a unique form of knowledge, one that modern critics have devalued by trying to separate the creator from his creation.