The Four Steps to the Epiphany: Successful Strategies for Products that Win

The book that coined the discipline of customer development and seeded everything "lean startup" later systematised. Blank's claim is that startups fail not because of bad products but because they sell to the wrong customers in the wrong way, and that the fix is a methodical process of learning about customers before scaling. The book is unpolished and repetitive — Blank self-published it because no editor knew what to do with an argument structured as a manual rather than a narrative. Read it as the more rigorous predecessor of Ries. For product direction the useful inheritance is the distinction between customer discovery (is there a problem?) and customer validation (will they buy the solution?) — a checkpoint most teams collapse into a single blurry "research" phase and then pay for.