https://en.wikipedia.org/wiki/Horizontal_and_vertical_writing_in_East_Asian_scripts
>>> After the success of the communist revolution in 1949, the People's Republic of China decided to use horizontal writing. All newspapers in China changed from vertical to horizontal alignment on January 1, 1956. In publications, text is run horizontally although book titles on spines and some newspaper headlines remain vertical for convenience. Inscriptions of signs on most state organs are still vertical.
What about the classics??? (books in PRC, Taiwan)
i can't imagine Confucius or Old Chinese poetry written
horizontally in a traditional-looking book.