R Hansen says: >I am not sure how you made this jump from a hypothetical question posed to make a point, but under the conditions stated, which choice would you make? Good parents or good books?
I've used the term "milieu" before to address the issues I presume you are trying to address with such a question. I learned a tremendous amount as a kid from my father, uncle, cousin, etc. without need for any books at all. It has to coming to understand the world as they saw it, playing games, solving little puzzles, estimating anything and everything just for fun, being told "cool things" like how light waves work as interacting electro and magnetic fields, etc. On the other hand going to the library together every two weeks was a family institution, at first in our neighborhood and later at the beautiful main branch of the Carnegie. In the library I was free to explore on my own, but I'm certain the things I chose to explore were much influenced already.
I think your point was well made earlier -- almost everybody in this country can get good books if they are motivated to do so. The motivation is the much harder problem. But while it may be correlated to "class" as such its not determined by class. Something that money can buy, though, is more time with your kids, or at least proxies for family life like various enrichment activities.