They left Scientific American lying around a lot. The column that had the fewest prerequisites was Michael Shermer's skepticism column. Also, people around me kept trying to fix my brain, and when I ran into cognitive bias and other rationality topics, they were about fixing your own brain, so then I assumed that I needed to fix it.

In terms of religion stuff: My parents raised me with something between Conservative and Reform Judaism, but they talked about other religions in a way that implied Judaism was not particularly special, and mentioned internal religious differences, and I got just bored enough in religious services to read other parts of the book, which had some of the less appealing if more interesting content. (It wasn't the greatest comparative religious education: I thought that the way Islam worked was that they had the Torah, the New Testament, and the Qur'an as a third book, sort of the way the Christians had our religious text as well as the New Testament as a second book.)