I learned quite quickly from engaging great texts that there was more to them than just plot and surface symbolism. My Literature teacher in high school inculcated in us this means of analyzing, of digging deeper into text and reading in between the lines. When I began doing that, the things I could see in a given text were remarkable. The first work I read under this lens was the assigned work at the beginning of Senior year Literature: Macbeth. The things we found in Macbeth were incredible. Of course, these interpretations could not be found on Sparknotes and they could not be found on the play's Wikipedia page. Most of those interpretations were superficial: that Shakespeare meant exactly what he wrote or better yet, they came from a certain philosophical outlook on how to read: they were deconstructive and attempted to defile any traditional interpretation of the text or they were by-products of historicism, the view that there are no eternal questions and each thinker is merely a representative of the prejudices of his own day.
When Leo Strauss left his Neo-Kantian and phenomenological training in favor of studying Jewish and Islamic philosophy in the Medieval period, these types of reading (albeit deconstructionism was not on the scene yet) were the most common. The Hegelian idea that there are no permanent truths or questions but only truths or questions reacting to the dialectic of history had corrupted how philosophers read the Ancient and Medieval thinkers. These thinkers were to be understood historically and not philosophically. They were answering to a prejudice of their times, not an eternal question.
However, Strauss rejected this. He rejected the Hegelian understanding of history and gave the Ancients their footing. What he discovered in the Ancients was nothing short of a revolution. He re-discovered the art of esoteric writing.
What esoteric writing is, is exactly what my Literature teacher made us find in Shakespeare, the message in between the lines. The exoteric message was instead the lines themselves and their literal meaning.
Of course, many folks take issue with this. Why would Ancient thinkers do this? How do we know we're not reading our own prejudices into the text? The answer to the first question is because philosophers of the pre-modern era understood something which was lost in the Enlightenment optimistic understanding of man: that there should always be a dichotomy between philosophy and society. The two should intertwine, for sure, but they should never become one organism.
The reasoning behind that for the Ancients was simple: philosophy concerns itself with the permanent questions and contemplates them always with a reserve, a methodological skepticism. However, no society that wishes to function, can run on pure skepticism alone. Every society must have agreement about common sense beliefs, what the good generally is, and what it means to be human. It has no time for permanent questions, because society (unlike philosophy) needs its answers and cannot question forever. Therefore, the political mindset of society and the skeptical mindset of the philosopher should always be separate, for the good of society and for the safety of the philosopher living in a society dominated by a somewhat necessary dogmatism.
To prove his theory, Strauss analyzes three texts of Jewish philosophy: Maimonides' Guide for the Perplexed, Judah Halevi's Kuzari, and Baruch Spinoza's Theologico-Political Treatise, each of which he finds esoteric writing in. The justifications and methodology differ by author: Maimonides' esotericism was birthed from Rabbinic teaching that the true teaching of the Torah should not be written haphazardly, for it could be misunderstood and misappropriated by the vulgar and so the best way to write candidly about The Torah was to create a message that could be understood and used appropriately by the vulgar (the surface thinker) and could be dissected by the wise (read esoterically). Maimonides seems to imply many things, when read esoterically, that question the status quo of Judaism in the 13th Century. Halevi, on the other hand, seems to claim many things about the relation between theology and philosophy that would have been uncomfortable for the Medieval man. Similarly, Spinoza writes the deeper messages of his naturalism into what may seem pious writing, but which underneath imply an even deeper materialism than his pantheism understood proper.
When the Great Books are understood this way, as layered, as possessing writing between the lines, as being testing grounds for the minds of their readers, they inevitably become more important for us. In a time when Great Books are often devalued as being the senseless by-products of history or the pious renderings of a dogmatic age or as being irrelevant in the eyes of modern science, Strauss's understanding of how to read properly can be of great insight for maturating thinkers and a great source of the debates of the Western tradition. The old phrase that "God is in the details" certainly comes true when it comes down to serious intellectual inquiry.