Problem–Solution Fit
Evaluates whether a real, painful problem exists and whether the proposed solution is meaningfully desired.
When to use: Before committing to a solution or roadmap.
Are we building the right product?
Validate product decisions before hiring, scaling, or committing long-term cost.
ProductBooks is an evidence-based product validation system that helps founders and product teams determine whether they are building the right product before committing significant resources. Instead of relying on opinions or assumptions, ProductBooks uses structured evaluators to assess your product decisions against real evidence from real users.
ProductBooks may tell you to stop.
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No sign-up required. Results are immediate.
Common Product Failure Patterns
Most product failures share the same root causes.
- Building features without a validated problem
- Confusing usage with real value
- Scaling before economics are proven
Start with the earliest stage you have evidence for
Each evaluator provides evidence-based scores, clear verdicts, and concrete next actions.
Product–Market Fit
Evaluates evidence of repeatable demand, retention, and willingness to pay for the product.
When to use: When users exist, but adoption and retention are unclear.
Business Model Fit
Assesses whether the business model can sustainably support the product and market it serves.
When to use: Before hiring, scaling spend, or fundraising.
Fit Report Generator
Generates a single, investor-grade ProductBooks Fit Report by synthesising all ProductBooks stage outputs.
When to use: When you need a single, investor-grade summary.
These tools are free and standalone. ProductBooks brings them together into a single system for continuous product decision-making.
Join the ProductBooks waitlistWhen to use ProductBooks
ProductBooks is designed for critical decision points in a product's lifecycle. Use it when you need to determine whether your product decisions are backed by real evidence rather than assumptions.
- Before committing to a product roadmap or solution direction
- When you have users but are unsure about real adoption and retention signals
- Before scaling spend, hiring, or fundraising based on assumed product-market fit
- When you need an objective, evidence-based assessment to share with investors or boards
Learn more about how ProductBooks fits into evidence-based product development in our learning centre.
Product Fit Cascade
ProductBooks enforces the order teams must validate to avoid false confidence.
- Problem–Solution Fit — Are we solving a real, painful problem?
- Product–Market Fit — Do users adopt and return without pressure?
- Business Model Fit — Does the product support a viable economic model?
What ProductBooks Produces
- Clear stop / continue signals
- Evidence before scale or spend
- Alignment across product, market, and economics
How ProductBooks interprets results
ProductBooks does not offer opinions or coaching. Each evaluator applies strict, predefined evidence definitions to the information you provide. Evidence that meets the definitions is scored. Evidence that does not meet the definitions scores zero.
This means results are reproducible and objective. Two different teams submitting the same evidence will receive the same scores. The system is designed to surface gaps in your understanding, not to confirm what you already believe.
Read the full evidence definitions to understand exactly what qualifies as scoreable evidence across all three evaluation stages.
System Fit
ProductBooks defines what must be true before GrowthBooks scales, PeopleBooks executes, and ProfitBooks optimises.
Who ProductBooks is for
This is for founders who
- Are making product decisions under uncertainty
- Want evidence before scale
- Prefer clarity over speed
This is not for
- Feature-driven roadmap builders
- Teams seeking tactics without validation
- Companies avoiding economic truth
Get started with ProductBooks
ProductBooks exists for founders who understand that what you choose not to build matters as much as what you do. This is a long-term system for serious decision-making.
Run a free evaluator