Paul Theroux lives in Hawaii and on Cape Cod... when he's not traveling. And Paul Theroux travels a great deal, having made his literary reputation on the road, starting with The Great Railway Bazaar (Houghton, 1975), the story of a train trip he took in 1973, which was hilarious, irreverent and stowed in every backpack on three continents.

Fast forward 33 years, and he's still traveling and writing about it—this time, to quote the subtitle of his new book, Ghost Train to the Eastern Star (out this August from Houghton Mifflin), “28,000 Miles in Search of the Railway Bazaar.”

Theroux, 67, has written 27 novels and collections (eight of them before Railway Bazaar) and 14 books of nonfiction. What motivated him, after all these years during which he's trekked the globe from Patagonia to China to Oceania and everywhere in between, to follow in his own footsteps? If he didn't do it, someone else—“like the punk I was in 1973”—might.

But more than that, he says, “I realize that the most revealing thing you can do as a traveler is to go back to a place you cared about and see it again, to see what time has done. You can learn from seeing the effects of human imagination or neglect.” His African trip, chronicled in the 2003 bestselling Dark Star Safari, taught him about going back. Theroux began his African sojourn young, serving in the Peace Corps in Malawi after graduating from the University of Massachusetts in 1963. (Twelve of that old Peace Corps gang meet every summer at his house on the Cape to cook and play bocce. “We talk a little about Africa, but mostly about ailments, deaths and divorce,” he says. “My wife takes off for New York, and we make a total mess.”)

He was originally planning another African journey even though, he says, traveling there is a challenge. (This from a man Vogue magazine has called “macho” and the Guardian headlined as “the Indiana Jones of American literature.”) “In India,” he explains, “you can end up in a small place and there will be a train or a bus and it will leave on a schedule, but in Africa you arrive in a place and the next question is, 'How do I get out of here?' And they say, 'maybe a truck will pass by' or 'maybe a missionary.' ”

When his family suggested he retrace the railway bazaar, he wondered initially if that would be interesting, because one thing Theroux does not want to be is a bore. He knows that repeating oneself is a symptom of aging, but he also notes that growing old “ is such a wonderful thing in terms of understanding the truth of the world, seeing the direction the world is going in, which you can only see by traveling. Places change,” he says, “but mostly you change.”

And so he set off from London, feeling as though he were a “ghost,” taking trains across Europe to Istanbul and through Central Asia (where everyone wants to emigrate to America), traveling east from India through to Japan and back across Russia on the Trans-Siberian Express. As always, he traveled alone, carried little and relied on the kindness of strangers, especially crossing the no-man's-land between borders. He wrote his travel notes in longhand, did crossword puzzles (“a total waste of time”) and composed short stories from ideas ignited by people and incidents he met along the way. He ruminated on political situations, local customs and internationally known writers.

In Japan, Theroux met up with Haruki Murakami and toured Pop Life, six stories of pornography in the Akihabara district of Tokyo. “I think that you see what a society is like, its personality, its character, by looking at its pornography,” he says. “It's different in every culture. The way a man treats a prostitute is the way he really is; he's not on his best behavior. If a Martian arrived on earth and had an hour to sum up this society, I'd send him to a porno shop.” Pause. “And then maybe to a restaurant.”