Paul Theroux may be the most irascible traveler since Tobias Smollett. Unfortunately, though, his anger never reaches the manic rage of that entertaining author, but devolves into whine and fret.

Setting out from his home in Medford, Massachusetts, one morning, Theroux begins a train journey that will take him down the length of South America, a continent not known for its kindness to dyspepsia. He finds much to upset him: The other passengers are boring, the food disgusting, and the trains filthy and decrepit…. When he finds a subject of some depth (his visit with Borges in Buenos Aires, the separation of Canal Zone blacks and whites into "gold" and "silver" races, down to the color of their coffins), he is vivid, moving, and precise. But there is, on balance, far too much petulance and showing off…. (pp. 42-3)

Theroux often quotes from the authors whose books he...