After piloting an emperor the age of a college student through China’s most drastic government reforms before the modern era, Wang Anshi retreated to his Halfway Hill villa at Nanjing, where in late middle age he became one of the Northern Song dynasty’s three or four most innovative poets. He redirected the craft of composing high-stakes policy papers into lighter-than-air evocations of clear-eyed grief, sensuous Buddhism, and intricate reactions to rain on the river or donkey-riding up Bell Mountain. Acrimony over his redesigned government, which he lived just long enough to see...