In 1975 Paul Theroux published a travel book, The Great Railway Bazaar: By Train Through Asia, that pushed him to the front ranks of the London literary scene. He had seven novels under his belt, including his early masterpieces Jungle Lovers and Saint Jack. But while his fiction had won him praise, it hadn’t brought in much income.

Railway Bazaar hit the best-seller lists, becoming the first in a series of travel memoirs that readers have lapped up for 30-odd years now.  Happy times, yes?

Well, no. The book came at a price that Theroux scarcely hinted at in its pages. His months-long absence from home, he says, put a big crack in his first marriage. He came back to London to find that his wife, resentful of his leaving, had taken a lover.

“I had not been missed,” Theroux ruefully remarks in his new book about retracing his old journey. “I had been replaced.”  Railway Bazaar, he adds, was written “in a fury”—an explanation, perhaps, for its zesty, crackling energy.

In Ghost Train to the Eastern Star: On the Tracks of the Great Railway Bazaar, by contrast, Theroux is contented on the home front and in transit. Older and happily remarried, he is as curious as ever about the people he meets and the places he visits on his 28,000-mile journey through Eastern Europe, Asia, India, Japan and Siberia.

Still, Ghost Train can be a sobering book. Brightly rendered and endlessly informative, it serves up one sharp, insightful anecdote or historical tidbit after another; and Theroux gamely puts up with delays, crowds, filth and occasional ailments as long as he feels he’s getting an unedited glimpse of the countries he’s in. Yet what has happened to some of those countries in the three decades since he last saw them is often unsettling.

Dictators have come to power, or held onto it for decades. You may be able to read elsewhere about Lee Kwan Yew’s oppressive, one-party micromanagement of Singapore (Theroux has a long history with the place). But Turkmenistan’s Saparmyrat Niyazov will probably be news to you, as he was to me.

While in power he banned beards, gold teeth and ballet, renamed the month of January after himself and April after his mother (he also tried to rename bread after her). He siphoned his country’s natural-gas revenue into his own pockets and erected gold statues of himself all over the place, demolishing much-needed housing in the process.

Theroux tells us all this while drawing sympathetic quick-sketch portraits of the brave, put-upon souls living under this insane regime.  In another vein, his journey through nearby Georgia—still, to Theroux’s eyes, establishing a fragile sense of independence after decades of Soviet domination—is more chilling than intended, given the recent headlines.

Then there’s the population explosion. Chennai (Madras) in India had a population of two million when Theroux was there in 1973; now it’s 11 million. A veteran walker, Theroux tries strolling down one of the city’s familiar main drags—and finds it impossible.

Any American traveling these days wants to gauge his country’s standing in the world. Theroux finds only two Bush supporters among the hundreds of people he meets. (A veteran of the Soviet Union’s failed campaigns in Afghanistan is especially doubtful about what we’re doing in Iraq and Afghanistan.)

But Ghost Star isn’t all somber. There are lively meetings with authors Haruki Murakami in Tokyo and Orhan Pamuk in Istanbul (“one of the most easily negotiated and hospitable cities in the world”). Thailand gives him great pleasure. Vietnam, he writes, is “reborn” after decades of war (even in 1973 he was impressed by its beauty—and is more impressed now by its population’s forgiveness toward Americans).

Hokkaido, Japan’s northernmost island, casts a spell on him. A happy reunion with a hotel-running family in northern Myanmar (also known as Burma) is entirely unexpected—although Theroux fully registers the oppressiveness of the military regime there.

Throughout the book, Theroux’s fresh phrasing is a treat, whether he’s evoking the desolation of rural Turkmenistan (“a landscape like cat litter”), the heat of Jodhpur (“like a glittering hammer”) or a massage in Bangkok (“a sort of samba along my spine”).

The ghost that haunts this trip is Theroux’s younger self, whom he addresses from time to time. But his more urgent focus is on a world that, with few exceptions, is taking a turn for the worse. “Only the old can really see how gracelessly the world is aging and all that we have lost,” Theroux writes.

The 33-year gap between his prose snapshots of the countries on his route makes for a telling double exposure.