The problem is that in order to do something without thinking about it consciously, you have to do it often. And you have to think about what you are doing as you learn to do it. The transition from conscious to unconscious behavior is subtle and few of us recognize when it happens. But it does. Now think about what is involved in reading.
Most people learn to read in elementary school, but few people are taught to read carefully.
The person who gets the most out of reading is the one who recognizes patterns, or relationships in the text. A good reader recognizes patterns. Looking for Patterns Reading something efficiently is a complex task because we can retain only a small amount of information in our short-term memory. So if you are concentrating on factual material, such as dates, or other kinds of numbers, you will not accomplish much. The reason is that most of the time facts are not useful in themselves.