Buying a stock at a discount can potentially set up investors for significant gains in the future. And one way to find undervalued stocks is by looking at their price-to-book ratios. If a stock is trading at or below its book value -- its total assets minus its liabilities -- that can mean that there's good value there for investors. But that's not always the case.

A business's assets may be overvalued and thus, the book value may not be all that relevant. And investors often discount a stock with a risky business, and stocks at deep discounts can sometimes end up becoming value traps .

Three stocks that are trading below their book values today are Tilray Brands (NASDAQ: TLRY) , Walgreens Boots Alliance (NASDAQ: WBA) , and Kraft Heinz (NASDAQ: KHC) . Here's a look at how far below book value they trade at, and whether they are really bargains or just value traps.

1. Tilray Brands

Canadian marijuana producer Tilray Brands is currently trading at a price-to-book multiple of around 0.4. It's a steep discount to book value but it's also not too surprising. Marijuana companies often incur writedowns as the value of their plants can change, which is why investors may not want to place too much importance on the book value when it comes to cannabis companies . That being said, Tilray Brands is definitely trading at a much more modest valuation than it has in the past. From a high of nearly $17 billion in 2021, its market cap is now around just $1.5 billion.

Bargain hunters may see opportunity at this reduced valuation, but there's plenty of risk. While the company did reduce its losses in its most recent quarter (which ended on May 31), from roughly $120 million in the prior-year period to just $15.4 million, the business still faces an uncertain path forward. It's burning through cash and has been relying on its alcoholic beverage business rather than cannabis to generate much of its recent growth.

While there's definitely some hope that Tilray Brands stock could jump if the U.S. legalizes marijuana, there's no certainty that will happen anytime soon. Given the question marks around Tilray's future growth prospects, its lack of profitability, and the low valuation likely being a key reason to buy the stock today, I would definitely consider this to be a value trap right now, rather than a bargain buy.

2. Walgreens Boots Alliance

Pharmacy retailer Walgreens Boots Alliance has also experienced a steep decline in its valuation. The stock hasn't been trading at its current level for decades. It is trading at 0.7 times its book value as investors have been significantly discounting this stock.

The company wrote down an investment it made in primary care operator VillageMD earlier this year, to the tune of $5.8 billion. Walgreens has been focusing on launching primary care clinics at its stores in an effort to boost traffic and generate growth, but it has proven to be a risky strategy thus far. The company continues to struggle with profitability and has incurred an operating loss in three of its last four quarters.

There's no doubt that Walgreens is a value trap right now. The business is in questionable shape and while the stock seems to look cheap, it always seems to find a way to become even cheaper, with many investors not seeing a reason to take a chance on the healthcare stock given the uncertainty the business faces.

3. Kraft Heinz

Kraft Heinz trades at just under 0.9 times its book value.

The company faces some risk due to inflation and rising costs making its brands appear much more expensive these days, especially when compared to private label brands. And a big problem for the business is that it has struggled to generate much in the way of growth. In the past four years, the company's top line has stayed between $26 billion and $27 billion. While the company's profits have increased during that time, the lack of revenue growth has made investors bearish on the stock.

Kraft, however, isn't as risky as the other stocks on this list and I'm more inclined to say it's a bargain buy rather than a value trap. Even though its growth rate has been underwhelming, the company has many strong brands in its portfolio and it has been looking at new ways to stimulate growth, including the launch of plant-based macaroni and cheese last year, and it's also working on getting its Lunchables brand into school cafeterias, which it says could be a market opportunity worth $25 billion.

Kraft's business isn't in trouble, but it does face challenges as it looks to find levers to pull to drive growth. But overall, it may still make for a good buy in the long run.

David Jagielski has no position in any of the stocks mentioned. The Motley Fool recommends Kraft Heinz and Tilray Brands. The Motley Fool has a disclosure policy .