Product Theory

I built my first two apps at 13—medical and productivity tools that became top sellers in their categories. I've been obsessed with what makes products work ever since.

By 19, I'd raised venture capital and built a productivity app that hit #1 globally. Forbes ranked it the top life manager in the world. Now I'm a founder at BuildBetter.ai, where I've talked to over 2,000 product people trying to understand what separates the products that win from the ones that don't.

As I was building products, I kept discovering patterns and lessons I'd never read in any book.

Some turned out to be known phenomena in other disciplines—things with names and research behind them that I'd stumbled onto accidentally. The IKEA effect: people value things they build, so adding steps to onboarding can actually increase engagement. Sunk cost as a design tool: investment creates attachment.

Others I discovered myself. Randomness in rewards—showing badges or confetti about 3% of the time—feels better to users than showing them more often. Too frequent and the dopamine flatlines. Too rare and they forget the reward exists.

Sometimes we do these things intentionally. Sometimes we discover them by accident, not knowing what they're called or that they're commonly understood theories. Sometimes it benefits users. Sometimes it benefits the company. Often both.

The more we know what's already known, the less time we spend guessing. The better we can apply what works, challenge conventional wisdom, and figure out what hasn't been tested yet.

Along the way, I've read what feels like every book about products—design, psychology, behavioral economics, business. Something was always missing.

Design books tell you how things should work. Great at taste, terrible at tradeoffs.

Psychology books tell you how people think, not what customers actually do. You finish knowing more and doing nothing different.

Behavioral economics books tell you how people act, but each one is a single theory stretched over a thousand pages. None of it feels directly applicable.

Business books are for executives navigating org charts and competitive strategy. Useful if you're running a Fortune 500. Less useful if you're trying to figure out why nobody's clicking your signup button.

Nothing bridged these worlds. Nothing took the why from psychology, the what from design, and made it immediately useful for building products.

This book is what I call Product Theory.

It's a collection of principles—the mental models I actually use when building products. Some come from design, psychology, behavioral economics, and business. Others I've discovered myself.

The book is organized into five sections: pricing, retention, choice, perception, and systems.

Every chapter follows the same structure. It opens with a story that makes the principle tangible. Then how to apply it. Then the research behind it. Finally, the limits—because no principle is universal.

Each rule appears right at the top, under the title. You can flip through the book and read just the rules if you want the compressed version.