Naperville Library Spy
A live look at what books are being checked out across the Naperville Public Library.
Wouldn’t it be really cool if…?
That’s how my projects start.
For the Naperville Library Spy, the story is a very personal one.
Ever since I got my library card sometime around 2016, I couldn’t believe libraries were a thing. I also couldn’t believe books could be interesting.
That sounds obvious to say, but it just never occurred to me.
The first books I checked out were Moonwalking with Einstein by Joshua Foer and The Power of Habit by Charles Duhigg.
I didn’t know English, and I thought to myself, “Well, a good way to learn the language would be to read books.” You can surely learn the language, but I didn’t know you could learn about ANYTHING IN THE ENTIRE UNIVERSE.
Did I read books before I came to the U.S.? Probably, but I can’t remember. I loved reading newspapers and magazines. But books, not so much. In the microcosm where I existed, books weren’t celebrated.
In the United States, public libraries exist in pretty much every city1. This is shaped by the belief that free access to books and information is a public good2. That sounds like a minor statement, but this is one of the most special things about this country3. Yes, Life, Liberty and the pursuit of Happiness are important, but so is the pursuit of knowledge to improve yourself, reach your goals, and ultimately reach enlightenment.
Libraries are vehicles of self-actualization. If you’re so lucky as to have that realization, your life will never be the same. You go to the library because you’re curious, much like how Alice’s curiosity makes her chase the White Rabbit. Curiosity is the foundation of all things. If you are not curious, you’re dead. When you follow your curiosity, you’re like Alice, you go and go and go, until the rabbit squeezes through a narrow opening in a tree, and she hesitates for a moment, just like you might, but she lets herself slip inside and reaches the subconscious. A world of dreams, of possibilities, of what you’re meant to do with the miracle of life you are.
By mere chance, I realized I could learn from books. People write interesting and useful things. Some of them write everything they learned. Some books are conversations and explorations. Others are voyages, like the very best voyages you will ever take.
And all of this … is just there, resting within walls lined with shelves, inside what we modestly call a library. It’s just there for free (well, not quite free because property taxes in Naperville are high), but you don’t reach for your wallet every time you check out a book.
Autopoiesis is a system creating and maintaining itself, and through reading, you participate in the creation of yourself.
One of the key moments in my life was the day I had the idea that I could learn English in one day. Of course, I didn’t. Then I told myself one week. Then one month. Then six months. By then, I was fluent. I learned that you can be ambitious, and things can happen much faster than you think. Progress doesn’t follow other people’s expectations. Most people told me it would take me years, or that I would be lucky if I even went to college.
I learned to think for myself. More specifically, I learned to set ambitious goals to see what would happen. If it fails, you readjust until you find the limit. Sometimes the limit is closer than you think.
This way of living led me to find the joy of the library. If books are interesting, magical, and useful, why not get more joy? So, that’s when reading a book a week came to me during high school. School has always been a petty society-forced inconvenience in my life, but I had to adapt. I would read for at least two hours a day. I would wake up at 6 AM, do 20 pushups, shower, and read for an hour. Then, before I went to sleep for another hour.
At a minimum, I was reading two hours a day. You can finish most books in 14 hours. Of course, I always had a book with me, so if there was time during the day, I would read more.
During high school, I thought lunch period was boring and way too long. I also didn’t know anyone, couldn’t communicate because I didn’t know English, and when I finally met some people, I thought they weren’t that interesting (I’m sure they were), but they were on their phones scrolling social media or playing random games. So I stopped going to lunch.
I’d go to the school library to read more books or take college classes. MOOCs were starting to become really popular.
By now, you’re probably thinking about two things: Did you not eat? And what about socializing, what about meeting people?
I did eat. I would just eat without the library people seeing me. The school had a dumb policy where you couldn’t go back and forth, so either you went to the library or lunch, but you couldn’t go back and forth, so to the library I went.
What about meeting people? What about my “social development”? I know I’m not supposed to say this, but on average, books are more interesting than people. At least at that point in my life. And no, I wasn’t this introvert who couldn’t look into people’s eyes or have a conversation. Sure, I could have a conversation, and would do things like join school clubs like the debate club and play sports like soccer and track & field. Eventually, I did go to lunch and would force myself to talk to people, but I found it boring and would often find myself reading Money Stuff by Matt Levine on my iPad.
During high school, I read one book a week, nearly 200 books in total. I learned so much from the library: about business, programming, science, philosophy, mathematics, finance, history, psychology, and so much more.
So much of what I am began there. I owe an incredible amount to that amazing, wonderful place we call “the library.”
After a while, I learned that you could place holds on books, and that was the coolest thing ever.
A hold is when you request a book, even if it’s checked out or sitting at another branch, and the library system sets it aside for you when it becomes available. It’s pulled from the shelf, or shipped from another location and waits there with your name on it until you come pick it up.
You could summon any book, any piece of knowledge, and boom, it would be waiting for you. You’d just walk in, and there it was.
Would it be really cool to see what other books people are reading?
Yes, it would. 4
Whenever I place holds, I’m always curious about what other people are reading. I like walking past the shelves where the holds are kept and seeing the stacks of books waiting to be picked up. You notice patterns: multiple copies of the same title, unexpected subjects, things you wouldn’t have searched for yourself.
I constantly get ideas for what to read next, and it’s genuinely really cool.
That is how the Naperville Library Spy was born.
The same curiosity that changed my life (and continues to change it) is happening all around us. Every hold placed, every checkout, every book waiting on a shelf. Someone else is chasing their own White Rabbit. I built the Naperville Library Spy because I wanted to see that curiosity in motion. Not just mine. Everyone’s.
📚👀Naperville Library Spy🕵️♂️📚
A live, unfiltered look at what books are being checked out across the Naperville Public Library
The site tracks real-time checkout activity across the Naperville Public Library’s branches and makes it visible.
Just books. Being read. In the real world.
Every checkout is a signal of curiosity. Every hold is someone deciding to learn something new.
The Naperville Library Spy turns that invisible stream of curiosity into something you can see.
Creating this site was fun, and I’ve learned a few things, which I wish to tell you now: (1) People are reading—far more than the narrative suggests, (2) there are curiosities and patterns in reading behavior you might not realize, and (3) this is a new way to discover books beyond algorithms and bestseller lists.
1. People Are Reading
There’s a narrative that people aren’t reading anymore.
The Naperville Library Spy shows the opposite. People are reading, and they’re reading a lot. According to the Naperville Public Library’s 2025 disclosures, the library saved patrons over $25,000,000.
I know last year, I requested books like Predator’s Ball, The Mottern Method, and Death in the Afternoon, and the library either had them, borrowed them from another branch, or acquired them.
I hope this website makes people want to read more!!!
2. Curiosities and Patterns
I’ve been running the site for a while now, and I’ve noticed a few patterns you might find interesting:
The 95th branch is the most popular by a lot.5
Movie and TV announcements immediately affect reading behavior. When a film or adaptation is announced, checkouts spike almost instantly.
Project Hail Mary is booming as its movie release approaches.
Books by Freida McFadden surged after The Housemaid adaptation.
I wouldn’t be surprised if The Odyssey dominates June, July, and August because of the upcoming adaptation by Christopher Nolan.
Branches have distinct reading identities.
As you might expect, different neighborhoods read different things. The overlap in the top 50 titles between branches is surprisingly low. Each branch has its own personality.
If you analyze checkout patterns carefully, you could optimize inventory distribution. If certain books are statistically more likely to be read at a specific branch, you could allocate more copies there from the start. That would reduce inter-branch transfers, lower transportation costs, decrease handling time, and improve availability for patrons.
Kids' books are massive.
Dav Pilkey is everywhere. He is so popular!!!
Dog Man is citywide, but led by 95th Street:
95th: 48.1%
Nichols: 34.6%
Naper: 17.3%
In the last 7 days alone:
Dav Pilkey was the top author
Dog Man was the top title
“Citywide consensus” books exist.
Some titles are almost perfectly balanced across branches. For example, Bob Books split nearly evenly: 7 / 8 / 6 across 95th, Naper, and Nichols.
True “always-on” repeaters are rare.
Only three titles appeared every day across the last eight calendar dates:
There are a few more interesting patterns, and I’m sure it’ll get more interesting as the days go by.
3. Another Way to Discover Books
Where do you get your ideas for what to read? Algorithms? Reading lists by politicians? The newspaper? Fake bestseller lists? Social media?6
Most of what we read, watch, and consume is filtered through recommender systems. Platforms suggest what to click next. Bestseller lists are curated. Influencers promote what’s “trending.”
What about getting inspired by your own neighbors?
Of course, what people say they read and what they actually read are often different. Projection, after all, isn’t only a mathematical construct.
Economist Timur Kuran calls this “preference falsification,” which is the idea that people publicly signal one set of preferences while privately holding another. We curate our identities. We project taste. But a checkout record is harder to fake. The Naperville Library Spy doesn’t capture what people claim to value. It captures what they actually choose.
The Naperville Library Spy is another way to discover what to read by seeing what people are actually reading.
The End
Wouldn’t it be really cool if you could see curiosity happening in real time?
It turns out you can.
Libraries are one of the few places left where curiosity doesn’t require permission.
No subscription. No performance. No algorithm deciding who you are.
Just shelves. And choice.
The library changed my life. The Naperville Library Spy is a way of watching it change others.
I love the library. I’m grateful libraries exist, and I hope you keep reading.
Read on,
Juan David Campolargo
UPDATE: The site has been archived. The Executive Director of the Naperville Public Library, Dave Della Terza, personally reached out and asked me to take down the site. The archive remains live so you can still explore the concept and see how it worked. It no longer displays real-time checkout activity. As it turns out, fiction is realer than you think.
The Institute of Museum and Library Services (IMLS) reports that about 97% of the U.S. population lives within a public library legal service area.
Public libraries are one of the most successful public infrastructures ever built.
And their history is interesting. Let me give you a summary.
Before public libraries, most libraries were private. Membership and subscription libraries were the norm. Can you imagine paying a subscription to a library? Oh, wait. Audible and Kindle. There were also libraries tied to churches, colleges, and private societies.
But there was a turning point in Peterborough, New Hampshire, in 1833, where the first modern public library opened to all and was funded by a municipality (tax-supported).
In the mid-1800s, cities started creating “free municipal libraries.” The Boston Public Library was chartered in 1848 and is often described as the first large free municipal public library in the U.S., which helped popularize the city-funded library model.
And then came Andrew Carnegie, who funded 2,509 library buildings worldwide, with 1,681 in the U.S.
Over 1600 libraries!!!
Carnegie was clever, and towns had to commit to ongoing local support. The building gift was meant to “force” the community to fund operations long-term.
Over time, libraries became a standard local government service. They’re often a city department, a county/regional system, or a library district with its own tax levy.
In most communities, the operating budget comes from local public money like property taxes.
The Naperville Public Library is taxpayer-funded, and the primary funding source is the local property tax. But it wasn’t always like this. In 1895, James Nichols leaves $10,000 to the City of Naperville to establish a library (explicitly so kids wouldn’t grow up without books). Three years later, the first Nichols Library opens.
This is the classic American pattern: a founding donor shows up → community decides it should be permanent → taxpayers fund it so it stays free and stable.
What public infrastructures of the 21st century will shape generations for years to come?
Can we talk about the Little Free Library? What an amazing invention!!!!!
The amazing Riley Walz inspired me, of course. Who doesn’t he inspire???
I don’t know how accurate this is. But according to my reports, 95th has ~54% more checkouts than Nichols and ~2.5x Naper Blvd.
Of course, if everyone is influenced by bestseller lists or social media, then those influences will still show up here. Reading behavior is contagious. If a book trends on TikTok or appears on a major list, people request it, and that signal appears on the site. In that sense, the Naperville Library Spy doesn’t escape the system; it merely reflects it.
But what makes it interesting is that it shows revealed behavior, not curated intention. As economist Timur Kuran has written about in his theory of preference falsification, what people publicly claim to believe or prefer can differ from what they privately choose. The site captures what people actually check out, not what they say they read. Even in a world shaped by algorithms, you can still observe the human layer underneath.
This is so fun!!! I am curious at how you put this resource together. How long did it take you from idea to product?
Asking people what book they're reading is probably one of my favorite question of all time (next only to which movie inspired them recently). Seeing people's behavior at scale is really fascinating. Like you mentioned, it reveals a lot about current trends and what people seem to care about in that moment of time. It is also interesting how people hear about these books and titles and the propagating network effect of it all. The website was a great way to visualize this data.
What new book recommendations do you have? And which interesting titles have you found as a consequence of making this website?