Recently, I was reviewing some fundamental analysis concepts that many investors overlook, and I realized there is a lot of confusion around net book value. It’s not the same as face value, and the difference is more important than it seems when you’re analyzing stocks.

Let’s start with the basics. Net book value simply refers to a company’s equity attributable to each share. If you break it down, it’s share capital plus reserves. The key difference from face value is that the latter is set only at the time the share is issued, while net book value is recalculated based on the company’s current situation. That’s also why you’ll see it called Book Value, especially if you read about value investing strategies.

Now, here’s where it gets interesting. Those who practice value investing are looking for exactly this: to find companies where the market price does not reflect what they’re truly worth according to their books. It’s like searching for inefficiencies in the market. When you calculate the net book value of a specific asset (a machine, a vehicle, whatever), you need to include amortization or depreciation—meaning that loss of value that naturally happens with use and over time.

The formula is simple: Assets minus Liabilities, and then divide by the number of shares outstanding. Quick example: a company has 3.2 billion in assets, 620 million in liabilities, and 12 million shares. The calculation would be (3.2 - 620) divided by 12, which gives you 215 euros per share.

But here’s the detail. The market almost never prices a stock at its net book value. Why? Because investors also factor in future expectations, market sentiment, and sector preferences. The market price is much more dynamic. That’s why the Price/Book Value ratio (P/VC) exists. You divide the current price by the net book value per share. If the result is greater than 1, the stock is expensive relative to its books. If it’s less than 1, it’s cheap.

Let’s take two fictitious companies. ABC has a net book value of 26 euros and trades at 84 euros. XYZ has 31 euros of net book value but trades at 27 euros. ABC’s P/VC is 3.23 (overvalued), while XYZ’s is 0.87 (undervalued). In practice, you see this in real companies: Acerinox showed ratios that indicated it was cheap compared with its book value, while Cellnex appeared overvalued. But be careful—a low P/VC doesn’t guarantee that the price will rise tomorrow. The stock market moves based on expectations, and if the economic context doesn’t cooperate, a company can stay at a low price for years without recovering.

Now, what are the limitations? The first is that net book value only counts tangible assets, ignoring intangibles. For software or video game companies, this is a serious issue. Creating a program is relatively cheap in terms of tangible assets but incredibly profitable. That’s why tech companies tend to have higher P/VC than other sectors, but that doesn’t mean they’re overvalued—it just means this tool doesn’t work the same way for everyone.

It also fails with small caps. New companies have a book value very different from their market price because you invest in them for their future potential, not for what they have today. And here comes something uncomfortable: creative accounting. Some accountants use legal techniques that make the results look better, overstating assets and understating liabilities. You can end up with completely wrong conclusions.

Bankia is the perfect example. In 2011, it went public with a 60% discount versus its book value. It looked like a bargain. Then the disaster followed, and in 2021 it was absorbed by Caixabank. This shows that the net book value of an asset—even if it’s positive on the books—doesn’t predict the future.

In fundamental analysis, net book value plays an important role, but it isn’t a magic solution. You need to combine it with macroeconomic analysis, sector conditions, company management, and earnings outlooks. It’s support for your decisions, not the decision itself.

The reality is that finding real opportunities requires more than just checking whether the P/VC is low. You need to understand the company’s competitive advantages, its position in the market, and the quality of its management. Net book value gives you a snapshot of the balance sheet at a specific moment, but that snapshot doesn’t tell you the whole story.