Theroux is my favorite travel writer. Easy to recommend all the books mentioned in this article, though The Great Railway Bazaar was my introduction to his way of writing about travel, and I think it's a good place to start.

All his train travel books are pretty similar in format (that's a good thing). He skips any discussion of famous landmarks and tourist destinations: he may or may not visit them, but he certainly won't be telling you about them. He spends a lot more time discussing the people on the train, the color of the city, the landscape going by, things like that. You would not read his books to plan a vacation, in other words. He gives (what I feel is) a very good representation of the character of the places he travels to, at least as he sees it. He's also very grumpy, or comes off that way, and his quick sketches of people (and hotels) are pretty funny sometimes.