How exactly is the Book of Changes divining?

Those fortune tellers are still using it.

However, the Book of Changes is actually not a divination book. It introduced the society, economy, science and technology, agriculture and astronomical phenomena at that time in detail, and divination was only a part of it. Before the Book of Changes, there were Xia Yi and Shang Yi, but they were all lost.

Its divination is actually an explanation of probabilistic events.