In his famous book the 4-Hour Work Week, Tim Ferris shares this theory that if you read 3 books on a topic from different authors, you’ll become more knowledgeable about it than 99% of people you know.
It’s a bold claim but it makes sense.
Tim’s not saying you’ll become an expert surgeon by reading 3 books on surgery. But you will gain more theoretical knowledge of surgery than most people (other than professional surgeons of course).
Three books rule might be the permission slip you were looking for to learn a new skill, to start a new career or to simply gain new knowledge.
The bottom line of the rule is that most people’s knowledge about any topic is very limited. If you have read three books (by different authors to cover more ground and to get different points of view), and have understood and internalized that knowledge, you already know more than 99% of people. In their eyes, you are an expert.