The Romance of the Three Kingdoms is not a great example. The particular section you've linked to is a Classical Chinese poem quoted in the introduction to the

The Romance of the Three Kingdoms is not a great example. The particular section you've linked to is a Classical Chinese poem quoted in the introduction to the novel. The rest of the book is (for the most part) written in Ming Dynasty vernacular Chinese (although it sometimes veers into a quite formal vernacular) and is actually kind of close-ish to formal modern Mandarin. The 20th century vernacular revolution didn't mean that written Chinese was exclusively Classical Chinese previously. All the famous novels of China (Romance of the Three Kingdoms, Journey to the West, Dream of the Red Chamber, Water Margin, etc) are all written in the vernacular of their time. It is nonetheless true that the overwhelming majority of writing that was not literature was written in Classical Chinese. As a side note, I would also rate Art of War as fairly readable (for a modern reader) Classical Chinese. Its excerpts are usually assigned at a middle school level in China. So "wasn't really meant to be easily read" feels a bit like a stretch. It is far easier to read (at least for me) than something like the Analects or the Daodejing. Classical Chinese still influences Chinese written works today. In order to fully understand modern Chinese literature, newspapers, legal documents, essentially anything at a register more formal than everyday Chinese, bits and pieces of Classical Chinese will filter through, to the point that I'd argue most readers of modern Chinese will gain a rudimentary understanding of Classical Chinese from reading the modern Chinese corpus.