The Principles of Product Development Flow: Second Generation Lean Product Development

Reinertsen writes the book most "lean" advocates should have written and didn't: a rigorous, economics-based account of why batches, queues and variability govern the speed of product development. The argument is quantitative — cost of delay, WIP limits, capacity utilisation curves — and often counterintuitive. Running teams at 100% utilisation destroys throughput; holding inventory has a measurable cost; smaller batches are almost always cheaper end-to-end than large ones. It is the deepest book on the page about why shipping faster is not about working harder. For a product director it clarifies the physics of the system you manage, not the psychology; dense, essential, worth re-reading every year.