Let's look at the book first. "Book" is a verb, meaning writing, which is what we often say today. The popular saying of "law" is laws and regulations.
Then combining "calligraphy" is the art of writing traditional Chinese characters in China according to certain laws and regulations.
The ancients said: you can only get it by taking the method, and you can only get it by taking the method. If you want to create a good work, it seems that you have to take the road of law.