I learned to read when I was three. (I probably figured it out from Sesame Street.) According to my mother, I was in a butcher shop with her when I read the brand name off of the refrigerated display case. A woman next to us turned to my mother and asked, "Did you know your daughter can read?" No, my mom didn't know that, but she's had plenty of opportunity to watch me read ever since.
Books are good for teaching you lots of facts, and yes, I've spent free time reading textbooks and encyclopedias. But there's more to books than facts; there's also fiction, getting to know people who never existed who live in places that never were. One of the things I love most about fiction is experiencing life through someone else's eyes. Doing so can help you develop empathy for others. For example, I didn't know much, if anything, about gays/lesbians before reading Gossamer Axe, but that book raised my sympathy for them.
Book aren't just brain food; they can feed your heart and soul too.