This e-commerce giant has good reasons to keep performing in the years to come.Amazon (AMZN 3.90%) has been a significant winner over the last two decades, generating enormous wealth for its investors.But for investors who have yet to buy the stock, is it too late now to add Amazon to their portfolio? Here are three questions to ask to answer that question: Is it a good business? Does it have good prospects? And is the stock price attractive?Is Amazon a good business?There are many ways for investors to evaluate a company's business model. Here are two elements to assess: customer captivity and barriers to entry.Customer captivity relates to the degree to which customers are loyal to a particular company or brand, making it difficult for them to switch to competitors. For Amazon, its customer captivity is reasonably high for several reasons.Image source: Getty Images.Take e-commerce, for example. Amazon is the largest e-commerce platform in the U.S., offering the most extensive selecti...
