Book value is a published estimate of what a vehicle is worth, derived from recorded transactions and adjusted for mileage, options, condition and region.
Different figures exist for different transactions. Trade-in value, private party value and dealer retail describe the same vehicle in three different contexts, and the gaps between them are substantial.
Estimates assume a clean title. A branded vehicle trades well below book, and the discount varies by brand and by how well the repair was documented.
Why it matters
It is the reference point for whether a price is reasonable, provided you compare against the right one of the three figures.
How to check it
Compare the asking price against private party value for a private sale, and adjust down for any brand on the title.
Does this apply to the car you are looking at?
Run the VIN or plate and see what is actually on record.
Related terms
Definitions are general guidance, not legal advice. Title rules, total loss thresholds and inspection requirements are set by each state and change over time, so confirm the position with the motor vehicle agency for the state the vehicle is titled in before relying on it.