I don't know anything about the methodology of this study about the role of books in the home, but the finding reached by Mariah Evans, an associate sociology professor at the University of Nevada at Reno, certainly grabs your attention:
This massive [twenty-year] 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.
Even having just a few books in the home seems to improve educational attainment, says Evans. But the larger the library, the greater the impact. Expect to see this study mentioned a lot in the book publishing business.