Concept
Continuous Discovery
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.
Continuous Discovery Habits
How this book uses it: Weekly customer contact minimum - interviews, observation, testing. Not "big research project then build for 6 months." Discovery feeds delivery, delivery feeds discovery in ongoing cycle. Make it sustainable by keeping interviews short (30-60 min).
Inspired
How this book uses it: Parallel to delivery, always testing ideas with customers. Schedule weekly customer interviews.