12 of the HARDEST Books Ever Written (and how they'll change you)

Added: 2026-05-30

[00:00:00]Most people think the difficulty of a book is a reason to avoid it. But what they don't realize is that the difficulty is the point. Over my more than 13 years as a peer-reviewed scholar and educator, I've come to believe that the hardest books ever written are hard [music] for a reason. And that reason is precisely what makes them so valuable.

[00:00:18]In this video, I'm going to walk you through 12 of the hardest non-fiction books ever written and show you exactly how each one dramatically transforms your mind. [music] So let's start with the first book because it is most definitely one of the hardest books ever written. Principia Mathematica by Alfred Whitehead and Bertrand Russell, published between 1910 and 1913. In this book, Whitehead and Russell were attempting to derive the entirety of mathematics from pure logical axioms.

[00:00:47]The result is a three-volume, nearly 2,000-page work written almost entirely in logical notation with ordinary prose appearing only to explain what the notation is doing. And here's something interesting that tells you everything you need to know about this book.

[00:01:03]Namely, that the proof that 1 + 1 = 2 doesn't appear until page 362 of volume one. And when it arrives, Russell adds a note saying the result is occasionally useful. Now before I go further, I want to be clear about how I'm measuring difficulty here because unlike most lists like this, I'm not just going by gut feeling. I'll rate each book on three axes, each out of 10.

[00:01:28]The first is linguistic difficulty, sentence complexity, vocabulary load, invented terminology. The second is conceptual difficulty, how novel the ideas are and how much prior knowledge is required. And finally, structural difficulty, whether the architecture of the book is especially dense or complex.

[00:01:45]And added together, that gives each book a total out of 30. And so what about Principia? Well, I would score it as a 29 out of 30, the joint highest on this list. But what does this book do to your mind? Well, it forces you to stop reasoning loosely. And most of us reason loosely without realizing it. We skip steps, we accept plausible-sounding conclusions, and we just fill the gaps with intuition. And spending serious time with even a portion of it changes what you'll tolerate in your own thinking. Now, that is one version of difficulty, brutal logical precision.

[00:02:20]But, the second book is hard in a completely different way. Hegel's Phenomenology of Spirit, published in 1807, is one of the hardest books philosophically. And it's a different kind of hard from Principia. You see, Hegel traces the entire development of human consciousness through a method called dialectics, in which every idea contains the seeds of its own contradiction, generating a higher synthesis, which then contradicts itself again. And he writes the way his ideas move in long, dense, self-consuming spirals. Bertrand Russell, the same Russell who co-wrote Principia, said reading Hegel made him feel as though he was going mad. And so, I find that pretty telling, coming from a man who spent years deriving mathematics from scratch. And so, I give this one a score of 27 out of 30. What it trains is the ability to sit with two opposing ideas at the same time without immediately forcing a resolution. And most of us can't do that. We just have to pick a side. But, Hegel teaches you that the tension itself is where the most interesting thinking happens. Once you can get through Hegel, you might think, "Okay, I've survived philosophical difficulty." But then, Martin Heidegger shows up and makes the problem even stranger. The third book here, Being and Time, published in 1927, asks, "What does it mean to be?" Now, he's not asking, "What does it mean to exist as a human being or something?" No, he's asking, "What is being itself?" And to get at this, Heidegger decides ordinary language just isn't up to the task. So, he invents a new one, Dasein, thrownness, being-toward-death, ready-to-hand. These aren't translations from German, they're actually new words for new concepts that didn't exist before. And so, I would score it a 26 out of 30 with the highest linguistic difficulty score on this list. Now, Heidegger is difficult because he makes language strange, but Immanuel Kant is difficult because he makes precision almost painful. The fourth book on this list, Kant's Critique of Pure Reason, published in 1781, goes hand-in-hand with Heidegger. Whereas Heidegger disorients you with invented language, Kant disorients you with precision. His central claim that the mind doesn't passively receive reality, but actively shapes it, and that space, time, and causality are structures the mind imposes on experience rather than features of the world, is so novel that his sentences become enormous just to explain it all precisely. And so, I would score it a 25 out of 30. Reading Kant forces you to slow down to a pace most people never read at, and that slowness, practiced regularly, actually sharpens how you think in every other area. In fact, in my undergrad, I took an entire course just on Immanuel Kant's philosophy, and it was a wonderful challenge precisely for this reason. But then, there's Ludwig Wittgenstein, who somehow wrote a book that's only about 75 pages long and still might take you longer to understand than some books 10 times its size. The fifth book here, Wittgenstein's Tractatus Logico-Philosophicus, published in 1921, consists of seven numbered propositions, each with sub-propositions arranged in a strict hierarchy. Wittgenstein is trying to define the limits of language itself, to show what can be meaningfully said, and what lies beyond the boundary of language itself. And it ends with perhaps the most famous line in 20th century philosophy. Whereof one cannot speak, thereof one must be silent. What makes this book so brutal is that Wittgenstein doesn't really fully explain his arguments here. Instead, he states them in compressed form and expects you to work out the reasoning yourself. And so, I'd give this one a score of 26 out of 30. Ultimately, what this book trains you to do is something simple to describe, but hard to build.

[00:06:15]Namely, the habit of not accepting a claim until you've actually followed the argument yourself step by step all the way through. And most people never do that. They accept conclusions that sound right. But Wittgenstein makes that impossible for you to do. And by the way, if you want to train yourself to further develop this skill, then feel free to watch my critical thinking masterclass at the link in the pinned comment below. Now, Whitehead is where things get almost unfair because he already appeared once on this list as one of the authors of Principia, and then he went and wrote another book that belongs here for a completely different reason. The sixth book on this list, Whitehead's Process and Reality, published in 1929, attempts a complete account of the nature of reality from scratch, covering everything from subatomic processes to human consciousness. And he invented an entirely new vocabulary to do it. And he explicitly tells readers not to read the book front to back on the first go because the later chapters are needed to understand the earlier ones. I would say this one scores 27 out of 30. But then there's Theodor Adorno, who is difficult in a way that feels almost intentionally hostile to the reader, which in a strange way is part of the point. The seventh book, Adorno's Negative Dialectics, published in 1966, is in my opinion, the most deliberately difficult book on this list. Adorno believed that clear systematic prose was itself a form of dishonesty. That the complexity of reality couldn't be captured in neat arguments without distorting it. And so, he wrote a book that argues against systematic philosophy while being systematic, and whose sentences regularly pull the rug out from under themselves mid-thought. I'll be honest, this is the book on this list I find most personally maddening, and I mean that as the highest possible compliment.

[00:08:07]I would say it scores 29 out of 30, the joint highest alongside Principia. And what I think this book really trains you on is the ability to sit with an idea without rushing it to a conclusion. Most of us, when we encounter a difficult idea, want some sort of resolution as fast as possible. But, Adorno trains you to stop doing that. And stopping that is definitely harder than it sounds. Now, Karl Marx belongs on this list for a reason people often miss. And no, it's not because you have to be a communist to read Marx. Instead, Marx is one of those writers who forces you to dig underneath the surface explanation of things. And so, the eighth book, Marx's Capital Volume 1, published in 1867, surprises most people when they actually read it. Because, most people who have strong opinions about Marx either way have often never read Capital. This book is a dense work of political economy that requires you to hold Hegel's method and classical economics in your head at the same time. And it deliberately opens with its most abstract material first. I would say it scores a 24 out of 30. And what it trains you on is the habit of looking for the structural cause of a pattern before accepting the surface explanation. Why something costs what it costs. Why certain kinds of work get valued or devalued. Why a system produces the outcomes it produces. And whether or not you agree with where Marx lands, that way of interrogating a situation is genuinely powerful. And once again, I'm sorry I have to say this, but no, just because you read Marx doesn't make you a Marxist. It makes you well-rounded. Now, the ninth book on our list is very different because instead of pushing you into economics, logic, or metaphysics, it brings you back to something much closer and easier to overlook, your own body. Merleau-Ponty's Phenomenology of Perception, published in 1945, is perhaps not as well known as many of the others on this list. His central claim is that the body thinks before the mind does. That perception isn't raw data the mind just interprets, but is already a form of understanding in itself. And I wish I had more space in this video to elaborate more on this very important book. But for now, let's just say it scores a 24 out of 30 for me. What it trains is the habit of noticing how your physical state, your posture, your fatigue, your environment, is already shaping your reasoning before you've consciously formed a thought.

[00:10:30]Now, Thomas Kuhn is probably the easiest writer on this list to read sentence by sentence, but that's exactly why it's dangerous because you can feel like you understood it long before you've actually absorbed what it implies. The 10th book on our list, Kuhn's Structure of Scientific Revolutions, published in 1962, is the most readable book on this list, and I want to be careful about saying that because readable doesn't mean easy. It scores 20 out of 30. The thing is, you think you understand it as you read it, but then you sit with it for a few days and realize the implications go much further than you grasped. Kuhn is arguing that scientists working in different paradigms literally cannot understand each other, that entire frameworks of understanding get replaced wholesale, not refined gradually. And what it trains you on is a permanent suspicion of consensus. You start asking what the current framework can't see rather than just working efficiently inside it. And that question, once it becomes a habit, changes how you approach almost any field. And if Kuhn is deceptively readable, Baruch Spinoza is the opposite. When you read his work, you know immediately that you're entering something pretty strange because it doesn't even look like what you think of as normal philosophy. The 11th book here, Spinoza's Ethics, published in 1677, is written as geometry, literally.

[00:11:50]Definitions, axioms, propositions, proofs, corollaries, in the same format as Euclid's Elements. You have to learn how to read it before you can read it, which is a problem no other book on this list, except maybe the Principia, presents quite so bluntly. And finally, we get to the 12th book on our list, a book that probably more people have attempted than almost anything else here. Partly because it looks playful and then becomes one of the most difficult intellectual experiences you can put yourself through. Douglas Hofstadter's Gödel, Escher, Bach, published in 1979 and winner of the Pulitzer Prize, is one of the hardest books out there. On the surface, it's about three things. Gödel's incompleteness theorems, Bach's fugues, and Escher's self-referential drawings.

[00:12:37]But those are just the entry points.

[00:12:39]Hofstadter's actual argument is about consciousness itself, and specifically about how self-referential loops in formal systems might give rise to a self. I would say it scores a 24 out of 30. And the way it achieves this score is by dragging you through mathematics, music, and visual art all simultaneously, forcing your brain to find connections across domains it would never normally put together. And as research suggests, this kind of cross-domain thinking, which every book on this list also [music] forces you to engage in at some level, strengthens connectivity across brain regions in ways that [music] staying inside a single domain simply does not. If you want to keep leveling up your critical thinking to make a massive impact not only on your own life, but also on the lives of countless others, then be sure to watch this next video.