Explain what book it is in concise language. What is it about?

The Book of Changes is a divination book.

But its mysterious form contains profound theoretical thinking and simple dialectical ideas.

Zhouyi Ancient Classics was written in the Yin and Zhou Dynasties. This is a step-by-step divination book, which begins with a certain divination method, that is, using the changes of 64 hexagrams and 384 hexagrams to predict good or bad luck. This indicates that the ancients began to realize their own strength and turned from superstition to scientific human awakening, which is a cognitive system of science and superstition. Confucius, a sage in the Spring and Autumn Period and the Warring States Period, and his disciples were familiar with Zhouyi Ancient Classics, and created The Book of Changes, which carried forward the philosophy contained in the divination, made the Book of Changes a book full of great philosophies about the universe and mankind, and marked the new awakening of mankind that philosophy was born out of theology. Since Emperor Wu of the Han Dynasty deposed a hundred schools of Confucianism, Zhouyi has become the first of the Six Classics (Poetry, Calligraphy, Rites, Music, Yi, Spring and Autumn) and the first representative work of China traditional culture. In a word, The Book of Changes, including classics and biographies, is an important classic full of the wisdom of ancient people in China, which emphasizes divination and philosophy.