In my whole life, I have known no wise people (over a broad subject matter area) who didn’t read all the time – none, zero.
This is the best advice I can currently muster: read plenty of non-fiction books.
I enjoy fiction too, but find non-fiction more useful because it helps me build an intuition for and understanding of the world I live in. Which, as it happens, is plenty interesting.
Just remember that reading, like mathematics, is not a spectator sport. You need to engage with what you read. Ponder it, question it, compare it, and use it. The goal is to learn, not to race through as many books as possible.
There is nothing original about this advice (so it’s probably safe):
07:30 A speech
08:00 Reading a historical work
09:00 A speech
10:00 Dictating letters
11:00 Discussing Montana mines
11:30 A speech
12:00 Reading an ornithological work
12:30 A speech
13:30 A speech
14:30 Reading Sir Walter Scott
15:00 Answering telegrams
15:45 A speech
16:00 Meeting the press
17:00 A speech
23:00 Reading alone in his car
24:00 To bed
Warren [Buffett] and I do more reading and thinking and less doing than most people in business. We do that because we like that kind of a life. But we’ve turned that quirk into a positive outcome for ourselves. We both insist on a lot of time being available almost every day to just sit and think. That is very uncommon in American business. We read and think.
The problem with being too busy to read is that you learn by experience (or by your men’s experience), i.e. the hard way. By reading, you learn through others’ experiences, generally a better way to do business, especially in our line of work where the consequences of incompetence are so final for young men.
And I read a great deal, mostly biography.
[The two Moses boys] slept in the same room again, but adjoining their New York bedroom was their own library-study, its walls lined with books. Once Paul counted them; there were more than two thousand.
Ed Richards knew that Moses was brilliant—even “Five A” Johnson, who regularly received the top-grade in every course he took each term, said that Moses could have stood first in the Class of 1909 if he hadn’t spent so much time reading books that had nothing to do with his assignments …
Mortimer J. Adler and Charles Van Doren, How to Read a Book: The Classic Guide to Intelligent Reading (New York: Touchstone, )