Pilgrim's Progress uses rather ponderous 17th-century English, its complicated syntax heavily laden with religious quotations and allusions. Though the sentences don't exactly flow breezily for any reader, the diction and syntax may nevertheless sound distantly familiar to readers familiar with the King James Bible, whether because of its importance in Bunyan's day or its significant cultural impact even on modern English.
Obviously, Bunyan's use of allegory is a major element of his style that's impossible to miss. Allegory functions on every level, from the shape of the plot to the intricate theological meanings behind events to character and place-names. Even though the use of allegorical names seems very on-the-nose to modern readers, town names like Morality, Deceit, and Vanity and characters with names like Hopeful, Much-afraid, and Stand-fast convey the broad sweep of experiences and types of people one encounters over the course of one's life.
The near-constant sprinkling of biblical allusions into the story is another stylistic feature that no reader can ignore, even if they don't live in an era that's as saturated with religious language and imagery as Bunyan's 17th-century England. These quotations aren't meant to be heavy-handed (not primarily, at least!), but to convey a sense that life is suffused with spiritual realities and, more simply, that the Bible can be applied to any situation one meets.
The novel also uses dialogue to heighten drama and pull readers into the action while keeping narration and description to a minimum. Most conversations in the novel lack dialogue markers like "he said" and are instead written as if in a play, with headings like "CHRISTIAN" or "MERCY" or whomever the speaker happens to be.
