Concept
Minimum Viable Product (MVP)
2 books in the library reach for this idea - each in its own way. When independent authors converge on one concept, it usually deserves attention.
The Lean Startup
How this book uses it: Smallest thing that tests your riskiest assumption. Launch a landing page before building the product.
The Startup Owner's Manual
How this book uses it: Smallest feature set to test your value hypothesis. Build less than you think you need.