The problem with most arguments in the debate about reading is that they posit literature as an instrument used to achieve a certain goal: either the good of the individual (it is good for you) or the good of society (it makes you good). Leaving aside the issue of deciding whether what makes you good is not, ultimately, good for you, a more fundamental question arises: why does literature need to be defended at all?
The anxiety to justify literature is symptomatic of our age, when all activities should have an easily identifiable objective. The difficulty with literature, as well as with music or the fine arts, is that it has no recognisable purpose or, in Immanuel Kant's elegant formulation, it embodies "purposiveness without purpose". Reading certainly has myriad effects, but it is difficult to pinpoint exactly how it influences each person and harder still to translate this impact in terms of quantifiable gains.
Literature breaks the continuum of the everyday and makes us stop and think. The linguistic experimentation that is the hallmark of the literary estranges us from the most commonplace of tools, our language, while the fictional elements of novels, plays and poems offer us a glimpse into a reality that is not our own.
Several months ago, there was some article making the rounds that claimed some sort of proof for the idea that reading fiction made you a better person. I think it was Arts & Letters Daily that pithily remarked how, if that were true, English departments should then be oases of enlightened, saintly behavior. That's probably all the refutation it needs, but I'll add a pair of pennies: it's a progressivist delusion that the "bad" parts of humanity can be surgically excised, or selectively bred out of existence. Reading widely may increase the breadth and depth of one's understanding of human experience, but the basic elements of that experience will still include all the things moralists call vices or sins. Reading widely may increase the cognitive tools at one's disposal, without touching the perennial drives which motivate the use of those tools. All the condensed human experience and wisdom in the world won't eliminate the forks in the road that we all constantly encounter and put us on a direct path to perfection.