Reading a book doesnt necessarily exercise the mind. The vast majority of books are total junk. And, unlike weights, it is possible to become dumber by reading the wrong books. Spend four hours a day reading vanity press tripe and you would be better off spending those hours with netflix.

I have had students ask me how to improve thier english, how to sound smart. I tell them to stop watching american TV. Watch blackadder or upstart crow. Listen to people who are masters of the spoken word. Want to improve your writing? Stick to the classics. Dont touch JK Rowling until you are done with plato and shakespeare.

(Ive been watching a zew zealand series lately, learning all sorts of slang i didnt know.)