It’s a mark of Liz’s changing view of education that, in this passage, she can’t yet see the purpose of owning a set of free encyclopedias (when later she comes to work incredibly hard to get into Harvard). It’s not that Liz isn’t interested in learning about the world; rather, she believes that the most practical and, ultimately, most interesting knowledge isn’t found in a textbook. Liz is obviously a highly intelligent kid, but for the time being she doesn’t grasp the point of a formal education—she’s too busy focusing on survival.