A. J. Jacobs's Reading List

"I actually couldn’t find my copy, but I have a similar book. Basically, it’s a stand-in for any book by Martin Gardner . He is a superhero, a rockstar in the puzzle world. He was a columnist for Scientific American for decades. When you talk to puzzlers and mathematicians, it’s shocking the number of them who say that they fell in love with this area because of Martin Gardner’s columns. He would present what he called ‘recreational’ mathematics to show that math is not boring. Math can be fun. They’re logic puzzles, mostly. What I love about them is they’re the kind of puzzles where when you figure out the answer (or, often, read the answer, because I don’t get them all) you’re like, ‘Oh, yes, of course!’ It’s that feeling of, ‘I should have gotten that. I can’t believe I didn’t see that!’ That is a wonderful feeling. “Doing puzzles is like going to the mental gym” I’ll give you one example. There are two kids on bicycles and they’re 20 miles apart. They’re pedaling towards each other at 10 miles an hour. There’s a fly on the handlebar of one of the bikes that flies towards the other bike at 15 miles per hour. As soon as it hits the handlebars of the other bike, it flies back to the first one and keeps going, back and forth. The question is, ‘What distance does the fly fly in the time it takes for the bikes to reach each other?’ And when you first hear that, you’re like, ‘oh my God, that’s so complicated. How would I ever figure that out?’ The default method of solving it is to try to figure out how far the fly went on that first trip, then on the second trip and so on, and then to add them all together. That’s a super complicated mathematical calculation, summing an infinite series. But what I love is that if you step back for a second and say, ‘Wait. What are we really asking here? Is there a simple way of working this out?’ the answer is yes. Because what you’re figuring out is how far the fly flies in the time it takes the two bikes to hit each other. And that’s pretty easy. The bikes are 20 miles apart, they’re each going 10 miles an hour so it will take them an hour to reach each other. How many miles does a fly go in an hour, if it’s going 15 miles an hour? 15. So it’s super simple once you see it. But when you are first presented with it, you’re like, ‘What the hell?’ That is a lesson I try to take to real life. What is the real problem? Don’t just dive in and start trying to go with your first instinct. Step back and say, ‘What am I really trying to accomplish here?’ Yes, absolutely. If you write a puzzle book without answers, you’re going to get into trouble. I write about this in my book. Back in the day, they did not provide answers in puzzle books. The most famous riddles of the Middle Ages are in a 10th-century book called the Exeter Book . It has about 95 riddles written by monks and there are no answers. A millennium later, there are still academics debating these riddles. ‘The answer is a team of horses.’ ‘No, it’s a candle.’ ‘No, it’s a bucket.’ They’re writing papers, going to conferences. I love that. Some could say it’s one of the greatest wastes of human mental energy ever, but I prefer to see it as a noble pursuit."

"This book is a collection of very clever puzzles. The author is mysterious and goes by the pseudonym M. Some are pictures, some are codes, and some are wordplay. One thing I love about them is that you have to use different types of thinking and solving techniques. One of my favorite puzzles is when you have to spot something that links a bunch of disparate objects or ideas. Finding patterns is the basis of science, it’s the basis of life. Here’s one with pictures, I’ll let you try and figure it out. That’ll be fun. What are these pictures of? Yes, but what kind of picture is it? Right. What about this one? I don’t know if they call it this in Britain, I think they do. It’s the one you’re not supposed to stick in your ear. Exactly. So what do those three pictures have in common? Yes, the solution to this one is letter. Each group of pictures has a common theme. Together, they spell out a sentence, which then reveals the solution. Even without the puzzles, I like the book for the writing alone. I love this line: “My preferred learning style has always been to jump off the cliff first and build a parachute on the way down.” I don’t agree with it. I think it’s a terrible life philosophy. But I love it. It’s so wittily expressed. M is a clever and funny writer. No, I came across it because (like you) I was always asking people what their favorite book puzzle books were. This book was a recurring theme. A lot of people love The Master Theorem . It’s colorful and artistic. Exactly. That is one of the themes, that doing puzzles is like going to the mental gym. You are building up ways of thinking and improving your reasoning and creativity. I buy it. Maybe it’s a rationalization because I’ve spent thousands of hours on puzzles. Maybe they do nothing for your brain. But there is some science that says that they teach you to think in better ways. I go all in and buy that 100%."

"I was 13 when this book came out in your country in 1981, and I fell in love with it. It’s one of the books that made me love puzzles. It’s a beautiful book. The illustrations are weird and delightful. Kit Williams was the artist and his style, I think, is beautiful. But what made the book a sensation was that within these beautiful drawings and these cryptic little stories along the side, were hints to the location of an actual buried treasure: a golden sculpture of a rabbit. It caused a mania worldwide. There were thousands of people in England just going crazy looking for the rabbit, digging up gardens, trespassing, getting arrested, knocking on the door of the artist and demanding to know the answer. He got thousands of letters; some were even threatening. This went on for about two years before someone finally figured it out. It was an incredibly hard puzzle, and the answer was obscure. It was a monument to… That’s right. It cast a certain shadow at noon on the equinox and if you dug there, you would find it. There was a scandal because the person who won might have cheated, they knew the author’s ex-girlfriend or something like that. Regardless, it’s a gorgeous book. I loved the idea of putting hints in a book that lead to a real treasure. The book spawned an entire genre of books called armchair treasure hunts, where people would hide things. There’s an American version called The Secret where the author buried 12 treasures around North America. It also inspired me. In my book, I have a secret code in the introduction. If you solve that code and put it into the website, then it leads to this crazy puzzle hunt, written by these two brilliant puzzle makers. The person who solved it won $10,000 and the contest took about a month. It is too late in one sense. In another sense, it’s not because you can still play the puzzles online at thepuzzlerbook.com. They are fantastic. You don’t even need to buy the book, though I hope you do. It’s free entertainment because these puzzles are brilliant. They were written by a team of professional puzzle makers led by a man named Greg Pliska. They’re so weird and delightful. They’re puzzles about the history of puzzles, so you’ll learn about that too. They don’t call it a treasure hunt. They call it a ‘puzzle hunt.’ But it is very similar. Going to the MIT Mystery Hunt was one of the adventures in my book. It’s where I met the people who wrote the puzzles for my contest. It’s a crazy annual event. It’s like an ironman triathlon for nerds. It’s 2,000 of the smartest people you can imagine, who come to Boston to the campus of MIT and spend 72 hours solving about 150 of the hardest, most baffling puzzles you can imagine. It’s a team competition and the team that finds the penny on the MIT campus wins. These puzzles don’t even have instructions. You will get a box of fortune cookies with strange symbols on the inside. You ask yourself, ‘What the heck is going on?’ And you try to figure it out. The answer is always a word. Once you get the word, you get the next puzzle. It’s hilarious and delightful."

"I read this book in college and I understood about 40% of it. I just looked at it again and maybe got up to 50% or 60%. It’s a dense book but it’s very playful. It’s hard to describe. It’s part history , part puzzles, and a lot of philosophy . His goal is to try to explain how a bunch of lifeless atoms can create consciousness . He uses all sorts of interesting metaphors. The atoms are like a colony of ants. The atoms in our brain are like meaningless letters, but you put them together and they gain meaning. There’s the idea that when you boil it down, some things are just axiomatic and don’t make sense except within the system. Part of the book is dialogues between Achilles and a tortoise. So it’s a very strange book but it’s full of delightful little nuggets. Even if you don’t understand the whole thing, there are so many little easter eggs, as we call them now, and puzzles within the book. There’s a complicated acrostic, where you take the first letter of each paragraph, and it spells out something about J.S. Bach. Get the weekly Five Books newsletter As I said, I’m a huge fan of paradoxes and recursion. As part of my book, I helped create the most time-consuming puzzle ever made. It’s a mechanical puzzle. It’s got 55 wooden pegs which you have to turn in a certain way. To finish it, you have to turn the pegs 1.3 decillion times, which is an unimaginably huge number. If you turn one peg per second, the universe will run out of energy by the time you solve it. The reason why it takes so long is that it’s a recursive puzzle. Hofstadter talks a lot about recursion, where you have to do the same thing over and over again. Think of a marathon where you run the first mile, and then go back. To run the second mile, you have to run the first mile again and then run the second mile. To do the third mile, you have to run the first mile, go back, do the second mile, go back, and then hit the third one. If you do a diagram of a recursive marathon on a piece of paper, the pages would reach higher than the Empire State Building. It’s all about these crazy exponential ways that numbers can get big. Our brains were just not built to understand numbers that go up like that. But they’re important. That’s why Covid spread so fast. We just were not able to comprehend how fast exponential phenomena can spread. You get a little bit of that, but if you want to learn about them, I recommend reading biographies. He just uses them because some of their ideas are interesting: Gödel’s Incompleteness Theorem, Escher’s paradoxical stairs, Bach with his fugues and repeating patterns. They’re in there, but they’re not the main characters."

"Yes, exactly. I discovered this because one of my favorite characters that I interviewed for my book is a woman named Elonka Dunin. She is obsessed with secret codes and ciphers and cryptics. So obsessed, in fact, that she moved states to be closer to one of her favorite puzzles. It’s called Kryptos and it’s at the headquarters of the CIA. It’s a sculpture that was created 32 years ago that is a cipher. It’s a big metal wall, carved with hundreds of letters. No one, not even the CIA, has been able to solve the cipher completely. They’ve solved parts of it, but no one has completely figured it all out. It’s one of the most famously unsolved puzzles in the world. People are obsessed and she is one of the leaders of the movement of obsessives who are online every day coming up with new theories. ‘Oh, I think the secret to the cipher is Dante’s Inferno ’ or ‘No, it’s the Navajo code talkers.’ Every day, there are new theories of how to crack this code, but no one’s been able to do it. I love the grit of these people who have been at it for 32 years and seem not ready to give up. I tell my kids, ‘Look at that grit ! You shouldn’t give up on your math homework after three minutes.’ Elonka Dunin teamed up with a German writer, Klaus Schmeh, who has a blog about cryptics and ciphers throughout history, and they wrote this book together. It’s a guide of how to break ciphers but you also get a lot of history, everything from World War Two to Roman ciphers. I just love it. Codes and ciphers are technically different. A cipher is when you have letters that represent other letters. A code doesn’t have to be letters. A code could be, ‘the snake is in the chicken coop’—meaning the enemy has got into the headquarters. It’s not about letters as much as it’s about disguising meaning. The most famous cipher is the Caesar Cipher, which you might have heard of because it was supposedly used by Julius Caesar in Roman times. It’s just a substitution where you substitute one letter for another. So you might move the letter over four spaces, so A might become D, B would become E and C would become F. That’s the one that we used as kids and you see on the back of cereal boxes. But that’s just the tip of the iceberg. From there, things get so much more complicated and delightful and weird. You can have Caesar ciphers that change with every word. There are zigzag ciphers where you have to arrange the letters in a certain way to be able to see them. There are just hundreds of ways to encode information and it’s not just for fun. Encoding information has been crucial throughout human history for everything from national security, and war—like the enigma code in World War Two—to love letters. In the 19th century, people would conduct love affairs by sending secret ciphers to each other via the classified ads. It was sort of like sexting in Victorian times. I know. You can see all the tragedy but also the triumphs. You can see it all in the history of ciphers. So I’m a big fan. It’s a fun book. Yes. I cast a very wide net of types of puzzles. My first love is crosswords and word puzzles. But there are also logic puzzles, Sudoku, and puzzle types I never even knew about but that are huge, like Japanese puzzle boxes. I was able to find these subcultures where people are obsessed with them, where it’s like a religion. They are as devoted to it as religious people are to their various denominations. What I loved was meeting people like Elonka, or the guy who solves the Rubik’s cube with his feet in less than 20 seconds. There are just so many characters who are delightfully weird and eccentric. It was so fun to explore not only the history of puzzles, but who these people are and why they love puzzles so much. Yes, the record is 3.5 seconds. It’s just mind-boggling. I can’t even twist it twice in 3.5 seconds. I definitely got into puzzles through the words. I am a word nerd. Crosswords were my first love. I don’t know if you read the intro to my book, but a few years ago, I was the answer to a clue in the New York Times crossword puzzle. It was the highlight of my life. My wedding was pretty good, but this was the holy grail. Then my brother-in-law, who did congratulate me, pointed out that I was in the Saturday puzzle. If you know the New York Times crossword, it’s the hardest puzzle of the week, and all the answers are really obscure. So his point was that this is not a compliment, it’s proof in black and white that no one knows who you are. So that was the emotional roller coaster that set me off doing the crossword religiously. I used to do it somewhat, but then I’d do it religiously hoping I would show up in an earlier part of the week, like a Monday or Tuesday. Which, as I mention in the book, I eventually did. Support Five Books Five Books interviews are expensive to produce. If you're enjoying this interview, please support us by donating a small amount . So words are my true love. But I grew to love all these other genres, including jigsaws, which I was very snobby about and looked down on. I was, ‘They’re not real puzzles.’ But I am a reformed jigsaw skeptic. I can officially say I am now a jigsaw lover. They’re very literary. So Tolkien, Harry Potter . Jane Austen had a lot of riddles. They are perhaps the oldest type of puzzle, and they are incredibly cross-cultural. Any culture from any time period has riddles. I do think they do get a bit of a bad rap, especially compared to their cousin, the joke. Jokes are considered much cooler than riddles. Even if you look at Batman , Heath Ledger won the Oscar for playing the Joker, but the Riddler is not as exciting a character. But I will say I gained respect for riddles because they can be poetry. It’s not just about solving the puzzle. They can be these extended metaphors that make you see life in a different way. Let me just read you one of my favorites. It’s from The Hobbit by Tolkien and I think it’s a lovely little bit of poetry. “This thing all things devours: Birds, beasts, trees, flowers; Gnaws iron; bites steel; Grinds hard stones to meal; Slays king, ruins town, And beats high mountain down.” The answer is time. I think it’s just a lovely, poetic way to think about the transience of things, that nothing is permanent."