You must know, for instance, whether you are reading fiction—a novel, a play, an epic, a lyric—or whether it is an expository work of some sort. Almost every reader knows a work of fiction when he sees it. Or so it seems—and yet this is not always easy. Is Portnoy’s Complaint a novel or a psychoanalytical study? Is Naked Lunch a fiction or a tract against drug abuse, similar to the books that used to recount the horrors of alcohol for the betterment of readers? Is Gone with the Wind a romance or a history of the South before and during the Civil War? Do Main Street and The Grapes of Wrath belong in the category of belles-lettres or are both of them sociological studies, the one concentrating on urban experiences, the other on agrarian life?

All of these, of course, are novels; all of them appeared on the fiction side of the best-seller lists. Yet the questions are not absurd. Just by their titles, it would be hard to tell in the case of Main Street and Middletown which was fiction and which was social science. There is so much social science in some contemporary novels, and so much fiction in much of sociology, that it is hard to keep them apart. But there is another kind of science, too—physics and chemistry, for instance—in books like The Andromeda Strain or the novels of Robert Heinlein or Arthur C. Clarke. And a book like The Universe and Dr. Einstein, while clearly not fiction, is almost as “readable” as a novel, and probably more readable than some of the novels of, say, William Faulkner.