This is very interesting. There is no fixed standard for being ugly. The same calligraphy, some people look ugly, and some people may look beautiful.
People who don't know calligraphy look beautiful, while those who know calligraphy feel ugly. How to define this? Obviously, this concept is not very rigorous, so there is a great controversy about ugly books.
In calligraphy terminology, calligraphy is generally evaluated by elegance or style, or directly from the perspective of technique. It is rare to say ugliness directly, so calligraphy is simply divided into two parts. But there is a kind of calligraphy that you can't describe simply by elegance and vulgarity. Beyond the scope of our evaluation. This is the ugly book I understand.
My understanding of ugly books mainly refers to modern calligraphy, which is the kind of calligraphy that is deliberately exaggerated and artificial purely for expression. Under the guidance of western theory, they are completely separated from the structure of Chinese characters and expressed purely by pen or ink.
The main manifestations of this ugly book are popular calligraphy style and modern calligraphy.