Convalescing from pneumonia one winter, Mary L. Daniels occupied herself by collecting all the digressions to the reader in the 47 novels of Anthony Trollope. Victorian fiction permitted a writer to stop in mid-story and expound his own views, and Trollope indulged this privilege with staggering frequency — together his digressions fill nearly 400 pages of close-set type, practically a novel’s worth in themselves. Some examples: “Throughout the world, the more wrong a man does, the more indignant is he at wrong done to him.” “A man cannot rid himself of a prejudice because he knows or believes it to...