Jeremy is completely right that there is no single best text for everyone. It depends on where you're coming from and what you want to learn. So I'll just give my experience.
Gregory Mankiw's Principle of Economics is a good text but has a noticeable leaning. His text was the first I used and I found it fairly useful in learning basic economic principles. It gave a relatively thorough description of some microeconomic concepts, but led me to be confused about how things like welfare and efficiency come into play when it's not really sensible to add together every participant's "dollar surplus" because for me a $10 consumer surplus means a completely different thing than a $10 consumer surplus for someone in poverty. The book led me to have fairly anti-government views that I later on recognized to be myopic. So ultimately, while it would make a good complement to a more balanced text, I would not recommend it as the primary source.
Instead, you should use Uncle Ben (Ben Bernanke)'s Principle of Economics (yes, basically all economics textbooks share the same title). I used it during a class taught by Christina Romer. I feel that it gave a much more balanced account of economics, and covered microeconomics and macroeconomics with more balance. In addition, it has many great examples (excerpts from the Economic Naturalist) that built intuition. I believe that the textbook (and those intuition-building excerpts) is the foundation of my economics studies. In addition, the financial crisis was just starting when the class began, so it provided great insight into the measures that Bernanke's team took to deal with the crisis. I found the context to be extremely helpful.
So in short, you should start with Bernanke's text if you're a beginner (I assumed that given your request for an introductory text), and once you have a stronger economic intuition, you can see what authors with different viewpoints think, so you can think critically about their opinions rather than accept them at face value.
Good luck! Economics is fun :)