I used Principle of Economics by N. Gregory Mankiw to teach myself introductory economics when I was a total pre-college newbie to economics. It describes the basics of economics clearly, is reasonably comprehensive and is a very easy read.

One textbook I would not recommend is Economics by Michael Parkin.This is the text I used for my actual introductory economics course at college. I thought its explanations were much less clear, and I often found myself returning to Mankiw's text to get a better explanation of the material covered in class.

Unfortunately, I have not seen Samuelson's book, so I can't compare either of these books to his.