"From the beginning, it was a silly idea. This, of course, I liked." So begins Night Train to Turkistan, Stuart Stevens's irreverent, irresistible Chinese travel tale. In the late fall of 1986, Stevens, a young political consultant and writer, invited three friends to join him on an unlikely 5,000-mile quest along China's Ancient Silk Road. Their goal was to retrace the steps of a famous journey made in 1936 by Peter Fleming, an eccentric...