I submit that really every part of China is worth seeing, not just Shenzhen, Shanghai, and Beijing. Sichuan, Guizhou, and Yunnan are very different from Guangdong and Fujian, which are not at all the same as Heilongjiang, Jilin, and Liaoning, which are so distinct from the Jiangnan, and on and on, to say nothing of the far west. Each Chinese province has roughly the population of an EU country; there may not be as many differences between each province as there are between European countries, but they’re still huge.
One can’t so easily find accounts of how much fun it is to travel around China. Those who haven’t ventured far beyond Shenzhen, Shanghai, and Beijing underestimate the sheer number of totally random stuff that happens to you. In stores, traffic, restaurants, and on the streets, I regularly come across behaviors and fixtures that I had no idea were a thing. You might be driving along miles of farmland, when suddenly a massive high-tech factory with the logo of a well-known foreign company looms up on the horizon; in a restaurant, I was asked one time to help with the cooking because chefs had to go out to buy more ingredients; you never know who might come up to you and tell you an interesting story. The lack of professionalism in nearly all things is sometimes frustrating but mostly hilarious.
That is from Dan Wang’s “What I learned in 2017,” many more topics at the link, including learning and books.