"For years, educators have thought the strongest predictor of attaining high levels of education was having parents who were highly educated. But, strikingly, this massive study showed that the difference between being raised in a bookless home compared to being raised in a home with a 500-book library has as great an effect on the level of education a child will attain as having parents who are barely literate (3 years of education) compared to having parents who have a university education (15 or 16 years of education). Both factors, having a 500-book library or having university-educated parents, propel a child 3.2 years further in education, on average. [...]
The researchers were struck by the strong effect having books in the home had on children's educational attainment even above and beyond such factors as education level of the parents, the country's GDP, the father's occupation or the political system of the country.
Having books in the home is twice as important as the father's education level, and more important than whether a child was reared in China or the United States. Surprisingly, the difference in educational attainment for children born in the United States and children born in China was just 2 years, less than two-thirds the effect that having 500 or more books in the home had on children (3.2 years)." source