Strictly for book nerds, Zunshine's book expounds on the application of Theory of Mind to literature. Theory of Mind is the activity of assigning a kind of reliability rating to information based on how that information was delivered to us. This involves "source tagging," in which we keep track of who said what, also called "metarepresentation."
Zunshine talks about the evolutionary importance of source tagging and how literature allows us to exercise our metarepresentative muscles. This is, for her, one of the chief pleasures of literature because it allows us the joy of using abilities that we have and gives us the reassurance that we are good at using them. Metarepresentation is so constant in our thinking that we are barely aware of its existence, but certain types of literature—like rich psychological novels and detection fiction—really take it out to the jungle gym for a workout.
My favorite part of the book was the section on Lolita. Zunshine explains that our minds can't deal with excessive unreliability, a situation in which almost everything is untrue. We aren't made to function in that type of environment. We are made to pick out individual statements of an obviously dubious nature. This explains why we are more likely to be skeptical of a friend who tells us our outfit is bad than of a stranger who tells us an astounding story about his identity with a straight face. And it explains why so many readers, past and present, continue to view Lolita as the story of a tempting nymphet rather than of a brutal pedophile. Every reader knows that Humbert Humbert is an unreliable narrator, but that doesn't keep many from still, still, absorbing his version of events. This is because Nabokov is such a damn good writer and uses every trick at his disposal to subtly encourage us to identify with Humbert's point of view. Zunshine takes us on a little history tour of the novel's marketing past as well, quoting editions and reviewers that claimed it was literature's "most authentic" love story.
Zunshine also tells of the reception of Richardson's Clarissa back in the day. Clarissa ended up as a kind of 18th-century Lolita in that readers failed to see through the author's all-too-clever narrative techniques. Richardson was so upset by readers' celebration of his loathsome protagonist, Robert Lovelace—an aristocratic lothario who spends the entire novel orchestrating Clarissa's ruin—that he actually rewrote the novel to make Lovelace more obviously villainous.
I should mention that the book is occasionally on the dry side. For those concerned about this, you may instead want to watch the video I ran into during an online search. Also a treatise on Theory of Mind and literature, it has the more promising title "Why Does Fiction Work? Hint: Boobs."