Product Theory
The Hidden Forces That Shape User Behavior
Spencer Shulem
A collection of principles—the mental models that separate products that win from the ones that don't. From psychology, behavioral economics, design, and hard-won experience building products used by millions.
Each chapter opens with a story, then the application, the research behind it, and finally the limits—because no principle is universal.
Spencer Shulem built his first two apps at 13—medical and productivity tools that became top sellers in their categories.
By 19, he'd raised venture capital and built a productivity app that hit #1 globally. Forbes ranked it the top life manager in the world.
Now a founder at BuildBetter.ai, he's talked to over 2,000 product people trying to understand what separates the products that win from the ones that don't.
Pricing & Value
Retention & Inertia
Choice & Decision
Perception & Positioning
Metrics & Systems
“This won't give you answers—every product is different. But it will give you the right questions.”
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Available February 15, 2025