The Search for Modern China by Jonathan Spence (1990) — The best single-volume history of China from the late Ming to the late 20th century, providing context for everything you see in Pingyao. The Shanxi banking system and the world it grew from are woven throughout Spence's narrative of Qing China.
Empire of Silver by Frederic Keer (2010) — A novel set in the world of the Shanxi banking families in the late Qing period, following a merchant dynasty as the piaohao system collapses under the weight of modernization and foreign banks. Fictionalized but grounded in the real history you'll encounter at Rishengchang.
China: A New History by John King Fairbank and Merle Goldman — Another essential overview of Chinese history, particularly strong on the Qing dynasty and the forces that eventually brought it down. The chapter on the commercial expansion of the Qing helps explain why a small inland city like Pingyao became a financial center for an empire.
A Single Shard by Linda Sue Park (2001) — For younger readers: a Newbery Medal novel about a Korean orphan and a master potter. Not set in China, but introduces the culture of East Asian craftsmanship and religious art that produced the sculptures at Shuanglin and Zhenguo temples.