You’re probably right that you can spend too much time reading “junk”. However, even “junk books” have positive effects. They increase reading comprehension and speed which is useful when you’re not reading junk.

Personally I also feel like books don’t “numb” my brain the way TV does. Sitting down with a book for hours, even “junk” doesn’t leave me feeling dumber the way watching hours of TV does. I imagine that reading activates higher order brain function a lot more than TV.