I'm delighted that my three boys and one girl have grown up or are still growing up in a house full of books in English, Chinese, German, and other languages. Sure enough, my oldest son makes a fine income as a hacker--but wait, I grew up in a house full of books too, and I've NEVER made as much money as he already makes.
A correlational study like this can't show us the path of causation, if any. Any behavior geneticist worth his salt would immediately ask, "Do the boys earn more as grown men because they had the home environment filled with books, or perhaps they gained genes from their parents that prompt both collecting books and pursuing more lucrative occupations?" And the answer to that question, of course, is both,[1] but anyway the genes will matter.
A correlational study like this can't show us the path of causation, if any. Any behavior geneticist worth his salt would immediately ask, "Do the boys earn more as grown men because they had the home environment filled with books, or perhaps they gained genes from their parents that prompt both collecting books and pursuing more lucrative occupations?" And the answer to that question, of course, is both,[1] but anyway the genes will matter.
[1] http://people.virginia.edu/~ent3c/papers2/three_laws.pdf