From one version ofthe Wikipedia page 
A Book from the Sky (simplified Chinese: 天书; traditional Chinese: 天書; pinyin: Tiān shū) is the name given to an art exhibition created by Chinese artist Xu Bing (born 1955). It was first displayed in Beijing's China Art Gallery in 1988 and created a sensation in the Chinese art community. The installation consisted of a set of books, panels and scrolls on which were printed thousands of characters resembling real Chinese characters, all devoid of semantic content. Xu spent years hand carving the typesetting blocks used to make the prints according to traditional Chinese block printing methods. Each block was embossed with a unique but meaningless symbol and then used to make the prints for the exhibit.
The work was originally titled An Analyzed Reflection of the End of This Century but the artist soon accepted the popularized title, A Book from the Sky. The work resulted in Xu losing favour with the communist government of the People's Republic of China and being vilified by some official critics as a "bourgeois liberal".
The Chinese idiomatic expression "天書" (celestial script) is a metaphor for incomprehensible writing somewhat akin to "chicken scratch" in English, referring to a writing system of unknown origins never seen before by mankind
Later versions of these characters incorporated English letters into square word-shapes, which he called Square Word Calligraphy.