Book value can mean:
- The net asset value of a company, determined by calculating total assets minus intangible assets (patents, goodwill) and liabilities. It is how much the company would have left in assets if it went out of business immediately.  Comparing the book value to the company's market value can indicate whether a stock is under- or overpriced.
- The value at which an asset is carried on a balance sheet. In other words, the cost of an asset minus accumulated depreciation.