All knowledge can be categorized in

All knowledge can be categorized into two types: theoretical and practical. Theoretical knowledge can be acquired from books, while you obtain practical one solely from experience. Although both types are important, I believe that experience is vital, whereas knowledge from books is merely useful.
Firstly, there are plenty of things that you will never learn to do until you make an attempt and actually do them. Let’s take swimming as an example. Knowledgeable as you might be about swimming, you will fail to swim without having had enough practice moving your hands and legs in water. Virtually all basic activities such as walking, talking, riding a bicycle, driving a car – to name but a few – definitely can’t be learnt from books.
Secondly, knowledge from experience is retained considerably longer than if you learn the same thing by reading about it in a book. It is always more effective to prove a mathematical formula by yourself than read about it in a textbook. You will never speak a foreign language unless you support learning rules by plenty of practice. I believe that all knowledge acquired from books should be reinforced by practical application of it.
Despite the fact that theoretical knowledge is of utmost importance, almost all vital professions rely heavily on experience. It’s unimaginable that an inexperienced doctor completes a challenging operation, even if he has read tons of books about medicine. The same is true about firemen: they train a lot in order to save people’s lives and it is impossible to replace their drills by theoretical lessons.
In a nutshell, I would prefer to say that “only something that is learned is contained in a book”. Yes it is very true that books are a precious resource for improving our knowledge as there are things that we can learn in no other way. Nevertheless, all educational books were written by someone who had got invaluable experience from the real life.