Getting Things Done: The Art of Stress-Free Productivity

Allen's book is the source of GTD — a personal productivity system built around a handful of simple disciplines: capture everything, clarify what it is, organise by context, review regularly, do the next action. Stripped of the mystique that later accreted around it, GTD is a clean protocol for the basic problem of having too much to do and no system for managing it. For product direction the book is useful not as personal productivity advice but as a clear example of a simple operational protocol that survives contact with reality. Most teams that have adopted parts of GTD (task lists with contexts, weekly reviews) did it without reading the original. Reading the original is still worth it.