The first month wasn’t easy. The Himalayas are punishing in early winter. ‘‘How exhausted we were with the fatigue of the day’s journey, how overcome by the rarefication of the air, the intensity of the cold, and how completely prostrated by hunger and thirst, is not easy to describe,’’ Das writes. Das’s guide is frequently drunk. Suspicions must be allayed everywhere. One village council permits his party to pass only after testing Das’s knowledge of Buddhism; even so, someone hollers, ‘‘That Hindu will surely die in the snows.’’ But Das makes it to Tashilhunpo, where he remains for five months, absorbing the news. China is flexing its muscle. Tibetans who rebuff a Chinese official’s attempts at extortion receive ‘‘four hundred blows with the bamboo.’’

Just before summer, Das departs for Lhasa, attired as a monk in dark goggles. For a while, he travels with a princess but falls so ill midway that she leaves him behind. Smallpox has seized Tibet, but Das finds only quacks to treat his fever. One night, he writes, ‘‘I felt so weak and ill that . . . I called my companions to my side and wrote my will.’’ Food is scarce, the hamlets of the Tibetan steppe are poor and miserable. Finally, one May evening, Das and his company trudge around a hill, and Lhasa reveals itself: ‘‘It was a superb sight, the like of which I have never seen. On our left was Potala’’ — the legendary palace — ‘‘with its lofty buildings and gilt roofs; before us, surrounded by a green meadow, lay the town with its tower-like, whitewashed houses and Chinese buildings with roofs of blue glazed tiles. Long festoons of inscribed and painted rags hung from one building to another, waving in the breeze.’’

We expect paroxysms of wonder from Das in Lhasa; instead, he turns all business, recording every conceivable detail: the dimensions of lintels, the tallow stirred into tea, the offerings at temples. He slips into Potala, joining pilgrims who have finagled an audience with the Dalai Lama, ‘‘a child of eight with a bright and fair complexion and rosy cheeks.’’ Lhasa is both squalid and grand, the filthy lanes of the inner city close by the magnificent 1,200-year-old Jokhang Temple and the majestic nine-storied Potala. One fat chapter in ‘‘Journey’’ explains Tibet’s political and religious hierarchies, the judiciary and the structure of taxation. This is Das pleasing his sponsors, singing for the supper he has already consumed.

In the end, Das lingers in Lhasa for only two weeks and returns, via Tashilhunpo, to Darjeeling. In a sense, though, he never leaves Tibet. He names his house Lhasa Villa, and he spends the remainder of his life translating Tibetan texts, compiling a Tibetan-English dictionary, thinking incessantly about the land he left behind.

The epilogue mars the tale. After the nature of Das’s trip was discovered, the Chinese persecuted anyone who assisted him. Tashilhunpo’s prime minister was murdered, his body thrown into a river. In 1903-4, a British expedition finally broke into Lhasa, and soldiers freed a former official, imprisoned for 20 years for helping Das. The old man, The North China Herald reported, blinked ‘‘at the unaccountable light like a blind man whose sight had been miraculously restored.’’ The analogy is impossible to miss: Tibet, too, had been released from China’s iron fist into the light. But much of this was ephemeral. Half a century later, China snatched Tibet back into its orbit; the Dalai Lama fled into exile. Only Das’s beloved Lhasa endures, the gleaming white walls of Potala still draped over their outcrop of rock like fresh snow upon a mountaintop.