Back in 2009, The Millions started its "Difficult Books" series--devoted to identifying the hardest and most frustrating books ever written, as well as what made them so hard and frustrating. The two curators, Emily Colette Wilkinson and Garth Risk Hallberg, have selected the most difficult of the most difficult, telling us about the 10 literary Mt. Everests waiting out there for you to climb, should you be so bold. If you can somehow read all 10, you probably ascend to the being immediately above Homo sapiens. How many have you read? What books would you add? Let us know in the comments!

Nightwood by Djuna Barnes - Dylan Thomas called Nightwood "one of the three greatest prose books ever written by a woman,” but in order to behold this greatness you must master Barnes' tortuous, gothic prose style. In his introduction to the novel, T.S Eliot described Nightwood’s prose as “altogether alive” but also “demanding something of a reader that the ordinary novel-reader is not prepared to give.” Nightwood is a novel of ideas, a loose collection of monologues and descriptions. What will keep you going: The cross-dressing Irish-American "Dr. Matthew-Mighty-grain-of-salt-Dante O'Connor," who, when not wandering Paris, drinking heavily, or dressing in nighties, rouge, and wigs of cascading golden curls, is expounding great rambling sermons that fill most of the book. These are funny, dirty, absurd, despairing, resigned—even hopeful in a Becketty I-can't-go-on-I'll-go-on kind of way.

A Tale of A Tub by Jonathan Swift - The first difficulty: The superabundant references to obsolete cultural squabbles (some obscure even in Swift’s eighteenth-century England) and then there’s the narratorial persona: an impoverished, syphilitic madman who cuts pieces out of his manuscript and his fellow citizens remorselessly. His compulsive digressiveness is deliberately baffling, but more baffling still is that this satire, aimed at “the Abuses and Corruptions in Learning and Religion” and written by a conservative, Anglican clergyman, ends finding nothing sacred. If you can bear it (and the 100s of footnotes you’ll need to understand its historical context), it’s the ultimate expression of cultural alienation and despair.

The Phenomenology of the Spirit by G.F. Hegel - Do you enjoy a good intellectual gobsmack every now and again? If so, Hegel’s your man and this book, a classic of German idealism and unquestionably one of the most important works of modern philosophy, is a fine place to start. Hegel’s refutation of Kantian idealism, history of consciousness, and quintessential explanation of the process of the dialectic is hard to understand and harder still to retain (“goes through you like lentils,” as one Stanford professor described it to me), due first and foremost to the breadth of its subject and its terminology. The book’s nearly impenetrable without a good edition and guide or two: The Oxford UP edition is widely considered the best (and don’t skip the notes and foreward) and the Routledge Philosophy Guidebook’s commentary by Robert Stern makes good warm-up reading; also good (and free) are J.M. Bernstein’s lecture notes for his UC Berkeley graduate course on the Phenomenology, available at BernsteinTapes.com.

To The Lighthouse by Virginia Woolf - In its intermingling of separate consciousnesses, Virginia Woolf’s fiction is both intellectually and psychically difficult. Not only is it hard to tell who’s who and who’s saying or thinking what, it is also disconcerting—even queasy-making—to be set adrift in other minds, with their private rhythms and associative patterns. It feels, at times, like being occupied by an alien consciousness. Some readers don’t ever find their sea-legs with Woolf.  The trick is to surrender yourself (true with other high modernists too), to let the prose wash over you and take you where it will—not to worry too much about understanding a dogmatic way.

Clarissa, Or the History of a Young Lady by Samuel Richardson - Richardson’s Clarissa is a heavyweight in more ways than one. The novel’s physical heft is part of its difficulty (she weighs in at just under three pounds in Penguin’s oversized edition), especially as her 1500 pages are light on plot (Samuel Johnson said you’d hang yourself if you read Clarissa for the plot). But what the novel lacks in plot it makes up for in psychological depth. Richardson was the first master of the psychological novel and he hasn’t been bested since. These depths are also dark and psychically wrenching: Clarissa's rejection and dehumanization by her monstrous family and the sadistic torments she undergoes at the hands of her rescuer turned torturer, the "charming sociopath" Robert Lovelace, offer some of the most emotionally harrowing reading experiences available in English.

Finnegans Wake by James Joyce -Finnegans Wake is long, dense, and linguistically knotty, yet hugely rewarding, if you're willing to learn how to read it. By this, I don't mean wallowing in the froth of scholarly exegesis the Wake churned up in its wake. Not the first time out, at least. (I take Joyce's talk about setting traps for his readers as an expression of hostility born out of years of frustration.) Rather, I mean surrendering to Joyce's music. Meaning here is more a question of effect than of decoding; in this way, this Difficult Book is paradigmatic of great literature more generally. Try reading 25 pages a day, out loud, in your best bad Irish accent. (Seriously - some of what seems like idiolectic obscurity is just a question of how you pronounce your vowels.) You'll be maddened, you'll be moved, and you'll be done in about four weeks.

Being & Time by Martin Heidegger - Being & Time is probably the hardest book I've ever read. To contradict what I said vis-a-vis Joyce, I don't feel comfortable as a reader of Heidegger letting things wash over me. Literary meaning and philosophical meaning are different beasts, and Being & Time, with its intentionally obtrusive neologisms, isn't meant to be dreamlike. It aims instead to be, among other things, a new kind of science, or a new foundation on which to build the sciences - an understanding of what it means "to be." Heiddeger gets a lot of things shockingly right, and yet the book's abstractness and rigor mean that most of his discoveries remain well-kept secrets. Even reading the first half in a graduate-level seminar, it took me over a year to get through this one. Was persevering worth it? Well, it changed my life. I don't know how much more a reader can ask for.

The Faerie Queene by Edmund Spenser - The difficulty and the pleasure of reading Spenser's masterpiece arise from a common source: its semiotic promiscuity. The Faerie Queene is allegory to the power of allegory. Or it is allegory drunk out of its mind on sugary wine, dressed up in layers of costumery, made to run singing through the garden of Eden at four o' clock in the morning before falling down in a heap at sunrise to make silver love to itself. Or it's the product of that lovemaking, tenor and vehicle copulating so variously and complexly that each becomes the other. There is much madness here, not least in the sheer hubris of Spenser's plan. (Like Heidegger, he only finished half of his magnum opus.) The Faerie Queene is also, bizarrely, a work of exquisite poetic control, hundreds upon hundreds of perfectly turned stanzas. I read it in college. It was hard as hell, and I forgot the plot even while I was reading, but many of its images remain burned into my brain ten years later.

The Making of Americans by Gertrude Stein - I've been working my way through The Making of Americans for many summers now. I keep getting several hundred pages in, switching to something else, and then, as with Heidegger, returning to find I've lost the thread. But what Heidegger describes, Stein evokes; to read even a page of The Making of Americans is to be thrown into a unique state of attunement. The fineness of attention its exquisite narrative tedium promotes is like an antidote to the shallows of the internet. Beyond the page, birds sing louder, sunlight grows thicker, car horns bare their souls. "The first stunningly original disaster of Modernism," someone wrote about this book, and while I'm not sure it was intended as a compliment, it makes me wish there were more disasters like this.

Women & Men by Joseph McElroy - In this space I could put any number of postmodern meganovels - a subgenre I've been smitten with for many years now. There's William Gaddis' JR, which is easier than people make it out to be, and Pynchon's Gravity's Rainbow, which is harder. There's The Recognitions and Mason & Dixon. There's William H. Gass' The Tunnel - verbally lucid, but morally arduous. Of the lot, though, I'd like to shine the spotlight again on Joseph McElroy's Women & Men. It is longer than any of the foregoing, and, in the idiosyncracies of its prose, on par with the hardest. Parts of it, anyway. Its temperament, though, is completely sui generis - warm, humanist, synthetic rather than analytic. As I wrote for the L.A. Times a few years back, it's like an entirely different version of what comes after Modernism. It's a weird and wonderful book, and I can't wait to dive into it again.

Garth Risk Hallberg is the author of A Field Guide to the North American Family and is a contributing editor at The Millions.