“”Sunt nobis nulla profecto Numina: cum caeco rapiantur saecula casu. Mentimur regnare lovem. (Trans.) In very truth there are no gods who govern mankind: though we say falsely that Jupiter reigns, blind chance sweeps the world along. ― Lucan. The Civil War.
Literature refers to written works, especially such forms as poetry, novels, novellas, plays, epistles, epic poems, graphic novels, haiku, speeches and letters. These may range from the Homeric epics to the speeches of Cicero and Martin Luther King Jr. Literature usually refers to the works that have had the greatest influence upon artists, culture, language and history. Literature traditionally was composed by an intellectual elite in most cultures around the world; literary traditions include Sanskrit literature, Mesopotamian literature, Latin poetry, Chinese philosophy, medieval English literature, Roman literature, Japanese haiku, et cetera. All of these elite literary forms are important to history and are considered a pleasure to read by many. There have also been many authors with wide audiences who are now highly regarded such as Charles Dickens, Leo Tolstoy, Mark Twain, George Orwell, Vladimir Nabokov, Fyodor Dostoevsky, Miguel de Cervantes and Anton Checkhov; these authors have had a large influence on many aspects of culture. What constitutes great literature is a difficult question that cannot be attributed to any one particular criterion; the surest benchmark is continual artistic and intellectual influence.
One of the most influential authors is William Shakespeare, who wrote elaborate language which surpassed his contemporaries, and he was influenced by masters of literature and philosophy that came before him such as Ovid, Montaigne and Seneca. Shakespeare was a rare example of a writer who wrote in a popular form of its time (the play), but the content surpassed the form to the point that he was highly regarded by artists and intellectuals. Although snobby critics rejected Shakespeare in his own time, poets and playwrights such as Pope, Dryden, Milton and Johnson defended Shakespeare's works and he continues to have a lasting influence on our culture. Along with his influence and his being esteemed widely by millions of people, Shakespeare has also been commodified and institutionalised since the late nineteenth century, and there is an entire industry of actors, playwrights, scholars and fans dedicated to his work. Shakespeare influenced hundreds of great writers, philosophers, composers, filmmakers, et cetera, and he introduced thousands of words into the English language; these factors make him a figure important to literary history and therefore worthy of study. 
Among the Western authors there have been many great skeptics who believed reason to be more important than doctrine, and many of them dared to question established dogmas of their period. Such thinkers include Lucretius, John Milton, Spinoza, David Hume, Schopenhauer, Nietzsche, Bertrand Russell and many others.
Some literature is an acquired taste, like warm dark beer. Try reading Moby Dick or anything by James Joyce, which are not as difficult as certain people think; yet they demand greater intellectual concentration.
Myriad literary theories exist, but most employ some variation of the scientific method (or can be argued to do so) in the process of analysis. Some of the more common modern examples include:
- Critical Historicism
- Psychoanalytic (Jungian or Freudian/Lacanian)
- Queer theory
The Argentinian writer Jorge Luis Borges (1899-1996) coyly suggested that all religions, in fact, derive from "fantastic tales". In 1790 the admirably crazy William Blake defined religion as "choosing forms of worship based on Poetic Tales". In North America, Walt Whitman (1819-1892) first titled Leaves of Grass as The New Bible. If you're interested in how religions work... *hint hint nudge nudge*. Though Whitman was hardly conventionally religious.
Many influential writers of literature were known for their rebellion against authority and religion. Although Greek and Roman epic poems contained gods and mythical beasts, Lucan, the Latin poet during the Nero regime BCE 39 65, was one of the first to dispense with the gods in his long and brutal epic poem De Bello Civili. This was a notable departure from the traditional use of Greek gods governing the affairs of humanity in Roman imaginative literature. The work proved influential for figures such as Dante Alighieri (who listed Lucan as one of the major poets with Homer), Percy Shelley, John Milton and Christopher Marlowe. Marlowe, who had collaborated with Shakespeare and was arrested for both atheism and sodomy, was one of the first poets of the Renaissance to translate the first book of Lucan’s notoriously challenging Latin into English. 
Percey Shelley (1792-1822), the husband of Mary Shelley, was a great atheist poet of the Romantic era. He wrote The Necessity of Atheism, and was booted out of Oxford for it. He influenced Karl Marx, Martin Luther King, Ghandi, Bertrand Russell, Leo Tolstoy, Oscar Wilde, Thomas Hardy, George Bernard Shaw, W. B. Yeats, Upton Sinclair and Isadora Duncan. He also influenced three or four generations of poets, including important Victorian and Pre-Raphaelite poets such as Robert Browning and Dante Gabriel Rossetti.
James Joyce, one of the most influential and scandalous authors of the twentieth century, was a non-believer who had been brought up catholic but gradually overcame his faith. His novel A Portrait of the Artist as a Young Man, influenced by Oscar Wilde, explores the cruel brainwashing that a young man must undergo in the highly conservative Catholic school system. The book dramatises the cruelty of priests who brainwash children to believe god will burn them in the underworld for eternity if they touch their doodles. Once the young man thinks critically and matures, he gradually loses faith and realises that his fears of sin and divine punishment were non-founded. With his newfound freedom, especially sexual freedom, he embarks on an artistic career and invents a new theory of aesthetics. The work is certainly autobiographical. Joyce greatly mistrusted the church and he was progressive for a man of 1920s; his work Ulysses contains heretical jokes, homosexual fisting, transgenderism, masturbation and oral sex, which made it the target of conservative critics (who didn’t even bother reading it) and censors.
Christopher Hitchens, an admirer of Joyce's Ulysses, wrote:
- Joyce admired the Jews because, like the Greeks, they lived in a diaspora and because, like Odysseus, they were wanderers. Furthermore, the Jews and Greeks proved that it was possible to worship higher goals without surrendering to the especial horror of Holy Mother Church—Joyce's lifelong enemy. He unceasingly blamed the priesthood for, among other things, the betrayal and abandonment of Charles Stewart Parnell, the heroic Protestant nationalist leader who was taken in adultery. Indeed, largely because of that church, Joyce himself was forced to live in exile from Ireland most of his life, and much of Ulysses is an attempt to reconstruct, from memory, the sight and sound and feel of his beloved Dublin.
A good deal of literature has a good amount of grounding in scientific and mathematical subjects. These include:
- Douglas Adams-Writer of the Hitchhiker's series. Friend of Dawkins. Heavy on fiction, but still fun.
- Edwin Abbott Abbott-Writer of Flatland, a novel using complicated mathematical concepts to satirize manners and society.
- The works of Lewis Carroll-Not just for kids, massively entertaining and contain many, many relevant logical puzzles.
- George Gamow-A physicist and friend of Einstein who wrote novels and humorous verse bringing both physics and its problems down to a conversational level.
- Terry Pratchett-Writer of the Discworld series. Probably one of the best fictionalizers of modern moral problems.
- Paradise Lost by John Milton constantly alludes to science, astronomy and the atheist Lucretius despite being a Christian epic poem. Milton met Galileo himself and writes in Paradise Lost that the earth travels around the sun. Satan's speeches are also deliciously heretical. Isaac Asimov was influenced by Milton and wrote an interesting analysis of Paradise Lost's science.
- Dante's The Divine Comedy may have an outdated cosmological system, yet the values are timeless. Dante states that the scientific method is important to our understanding of the universe, and his work was admired by scientists such as Galileo and Newton. The work influenced Michelangelo, Botticelli, Milton, T. S. Eliot and thousands of other figures.
- James Joyce alludes to astronomy, physics and atheism throughout Ulysses, especially in the Ithaca chapter in which everything Mr Bloom does, such as urinating with Stephen or making a cup of cocoa, is described in mathematical, scientific and cosmological terms. Despite the fact that Ulysses deals with an ordinary day in a man's life, the work has a grander cosmic impression created through allusions to science. The main character in Ulysses is also an atheist who questions religion.
- Lucan (1928). J. D. Duff, ed. Lucan: The Civil War. Loeb Classical Library. 220. Cambridge, MA: Harvard University Press.
- Eagleton, Terry (2008). Literary theory: an introduction: anniversary edition (Anniversary, 2nd ed.). Oxford: Blackwell Publishing. ISBN 978-1-4051-7921-8.
- Cain, William E.; Finke, Laurie A.; Johnson, Barbara E.; McGowan, John; Williams, Jeffrey J. (2001). Vincent B. Leitch, ed. The Norton Anthology of Theory and Criticism. Norton. ISBN 0-393-97429-4.
- Hume, Robert D. (1976). The Development of English Drama in the Late Seventeenth Century. Oxford: Clarendon Press. ISBN 0-19-812063-X.
- Hawkes, Terence. (1992) Meaning by Shakespeare. London: Routledge. ISBN 0-415-07450-9.