And I just thought of it today as I finished reading a very good book.
So what do I mean by "a very good book"? The subject is interesting and you will feel nourished by learning stuff that is not a waste of your time, stuff that is good for you (protein and not sugar or other worthless carbs). And the author is so engaging that his book is hard to put down. VERY important!
So, the book that I just finished reading today is David McCullough's The Wright Brothers. I have read other books by McCullough, and he can be very good; but he can also be not so good. It was an effort to read his 1776 even though I am primed for books of our Revolutionary period, especially "popular" books. Nevertheless, ... Also, his immediately previous book, The Greater Journey: Americans in Paris, young American artists in Paris in the middle of the 19th century, a subject in which I have little or no interest, was an absolute delight to read and revel in.
Of all the authors who write mostly about the American Revolutionary period, I am an especially big fan of John Ferling, who is always engaging and always hard to put down, despite (because of?) all the facts he puts before your eyes. Let me particularly recommend Jefferson and Hamilton: The Rivalry that Forged a Nation.