When selecting the core reading list for English or literature classes, there are certain criteria that are used, including the book's theme, its length, its content, its use of language, and determinations of its enduring value as a source of wisdom.
Obviously, one of the criteria that is most important is the individual's novel's complexity and appropriateness for different age groups. Many of the classics of American literature, including Steinbeck's Of Mice and Men, J.D. Salinger's The Catcher in the Rye, Mark Twain's The Adventures of Huckleberry Finn, and Harper Lee's To Kill a Mockingbird, all represent novels that have withstood the test of time in terms of the portraits they present of America during certain periods of time, the lesssons they can provide that remain relevant, and their superior writing. All of these examples are suitable for students in the 9th to 12th grades, but are less so for younger children.
Almost all books selected for English classes involve some type of conflict. Those conflicts may be physical altercations between characters, or they may involve contrasting personalities, for example, as is the case in John Knowles A Separate Peace, the relationship between Gene and Phineas, two friends whose friendship is marred by underlying currents of resentment on the part of Gene. In Steinbeck's Of Mice and Men, the conflict surrounding Lennie's mental disability and how he is perceived by others. Steinbeck's novel, as with Twain's and Lee's, portray the tragic implications of narrow-mindedness and ignorance on the part of large sectors of society. The lessons to be drawn, of course, involve tolerance and understanding, as well as the requirement for a just rule of law in a civil society. Those are lessons that remain as important today as when these classics of literature were published decades ago.
Of Mice and Men is routinely included in English curriculum for all of the reasons mentioned above. Its enduring importance, however, goes beyond what has been discussed. It provides a portrait, as with Steinbeck's The Grapes of Wrath, of an America experiencing difficult times, and how people responded to those challenges. These are themes that remain relevant. Combined with the superior writing styles found in these books, those themes ensure that these novels remain part of the modern curriculum.