Novels Taught in School Are Short

It's fair to say that not many writers' works and reputations survive for more than a generation or two. In a practical sense, writers in this country generally survive after their books--that is they stay in print--because they are taught in the classroom. Moreover, short books, like small dogs, live longer: Fitzgerald's The Great Gatsby and Hemingway's In Our Time and The Sun Also Rises are taught more frequently than Tender is the Night and For Whom the Bell Tolls, not necessarily because they are better but because shorter books are easier to get students to read and to teach. [ I doubt that Hemingway and Fitzgerald are taught in today's high schools and colleges.]  

Anthony Arthur, Literary Feuds, 2002