Most books fail not on the text but on demand. They answer a question nobody asks, or take on twenty established titles without an angle of their own. A viability score flips the order: validate first, then write.
Four signals, one verdict
The score condenses four dimensions into one number. Demand measures how often a topic is actually searched. Competition weighs the count and quality of existing titles. Price band shows what the market is willing to pay. And differentiability estimates whether there’s room for a new angle at all.
Demand — search volume and trend direction over 24 months
Competition — title density, ratings, recency of top sellers
Price band — realistic price range for the format
Differentiation — open angles, uncovered subtopics
Why a number is more honest
A classic market study gives you thirty pages that leave everything open. A score forces a decision. 0.87 means: write it. 0.45 means: differentiate or find another topic. That clarity is uncomfortable — and exactly why it’s valuable. It prevents months of work on a book the market never wanted.
A score doesn’t make the decision for you. It gives you the data to make it.
The score is a start, not an oracle
Data tells you whether a niche is open — not whether you have something to say. The best books emerge where a high score meets real expertise. The agent finds the gap; you fill it. That division of labor is the difference between a book that ranks and one that lasts.