Rob Fitzpatrick wrote a short, sharp book about one of the most common ways builders fool themselves: asking the wrong questions and believing the answers.
The core idea is simple. When you ask someone "Would you use this?" they almost always say yes — because they don't want to hurt your feelings. The Mom Test is named after the observation that even your mum will lie to you if you ask badly framed questions.
What the book teaches
The fix is to stop asking about opinions and hypotheticals, and start asking about behaviour and history. "Have you ever tried to solve this problem?" hits differently than "Would you pay for a solution to this problem?"
The questions that work are specific, past-tense, and about the other person's life — not about your idea.
Why it matters for engineers
Most engineers, myself included, are trained to build first and validate later. This book makes the case that a single well-run conversation can save you three months of building the wrong thing.
I read this while building 24hourscope and it changed how I think about which features to prioritise.
Verdict: Essential. Short enough to read in one sitting. Dense enough to revisit regularly.