The best way to use this book is not to simply read it or study it, but to read a question and stop. Even close the book. Even put it away and think about the question. Only after you have formed a reasoned opinion should you read the solution. Why torture yourself thinking? Why jog? Why do push-ups?

If you are given a hammer with which to drive nails at the age of three you may think to yourself, “OK, nice.” But if you are given a hard rock with which to drive nails at the age of three, and at the age of four you are given a hammer, you think to yourself, “What a marvellous invention!” You see, you can’t really appreciate the solution until you first appreciate the problem.