Behind the book
About
Hi, I’m Itai Bar Sinai. I’m a software engineer and tech entrepreneur with a math degree, and I’ve always been drawn to sharing the cool parts of mathematics with people who never thought of themselves as math people.
I now have a three-and-a-half-year-old at home, and a nine-month-old in tow. I wanted to make something like this for him — a real picture book about a real, beautiful, slightly mind-bending idea, told in a way a small kid can actually hold onto. So I made him this one, and put it online so other kids could read it too.
Why this book
I think of mathematics as the most rigorous form of philosophy we have: a way of asking the strangest, oldest questions humans have ever asked, and getting back answers that happen to be true. Hilbert’s Hotel is one of those answers, and it’s an unusually friendly one.
Kids are wired for paradox. Give a six-year-old a good one at the right age and you can watch something light up. My hope is that if curiosity towards big ideas — paradoxes, infinities, the occasional impossible-sounding answer — is sparked early, gently, with a smile, it doesn’t have to be unlearned later. That’s what I’m trying to do here.
What is Hilbert's Hotel?
Hilbert’s Hotel is a thought experiment by the German mathematician David Hilbert (1862–1943). Picture a hotel with infinitely many rooms, every room full. A new guest arrives at the front desk — and the hotel manager finds them a room anyway, by asking the guest in room 1 to move to room 2, the guest in room 2 to move to room 3, and so on, forever.
The point isn’t the hotel; it’s that infinity plus one is just infinity again, and that infinity isn’t a very large number — it’s a different kind of thing entirely. Mathematicians take the idea seriously enough that whole branches of the field rest on it. Six-year-olds, it turns out, are perfectly equipped to find it delightful.
How this book was made
The thought experiment at the heart of this book — Hilbert’s Hotel — is David Hilbert’s, not mine. This adaptation is mine: turning a century-old logic puzzle into a story for six-year-olds, choosing the characters, the structure, the voice, and the moments where the book lingers or moves on.
Both the illustrations and the text were made with help from AI tools, used deliberately and under tight editorial control.
Get in touch
For anything — questions, classroom requests, errors you spotted, kids’ reactions, or just to say hi — the easiest path is the contact form. If you’d rather use your own mail client, write to [email protected]. Either way it goes to a real person (me); please give me a few days to reply.
Press & reviews: same address. Mention “press” in the subject line and I’ll prioritise. High-resolution cover art and a short author bio available on request.